Biomass-resource-derived polyester and production process thereof

ABSTRACT

The present invention provides a resin capable of contributing greatly to solve environmental problems and problems related to exhaustion of fossil fuel resources and having physical properties suited for practical use. 
     The polyester according to the present invention has a diol and a dicarboxylic acid as constituent components and has an amount of terminal acid of 50 equivalents/metric ton or less.

TECHNICAL FIELD

The present invention relates to a biomass-resource-derived polyesterhaving a diol unit and a dicarboxylic acid unit as a constituent unit,and a production process of the polyester.

BACKGROUND ART

In today's society, paper, plastics, aluminum foils and the like havebeen used widely as packaging materials of various foods, medicines,sundry goods and the like in the form of liquid, powder or solid,agricultural materials and building materials. In particular, plasticshave been used in many applications such as bags and containers owing totheir excellent strength, water resistance, moldability or formability,transparency, cost and the like. Plastics used for such applications noware, for example, polyethylene, polypropylene, polystyrene, polyvinylchloride and polyethylene terephthalate. However, molded products madeof these plastics are neither biodegraded nor hydrolyzed under naturalenvironments, or have their markedly low decomposition rate, they mayremain in the soil when buried therein or spoil a view when discardedafter use. Even if they are incinerated, they may pose a problem such asemission of a harmful gas or damage to the incinerator.

A number of researches have been carried out on materials that arebiodegradable into a carbon dioxide gas and water by microorganisms inthe soil or water as a means for solving the above-described problems.Typical examples of the biodegradable materials include aliphaticpolyester resins such as polylactic acid, polybutylene succinate, andpolybutylene succinate adipate and aromatic-aliphatic copolymerpolyester resins such as polybutylene adipate terephthalate.

Of these, polylactic acid is one of the most typical polyesters but forit, an extremely low biodegradation rate is a big problem (Non-patentDocument 1). Polybutylene succinate, polybutylene succinate adipate andthe like having similar mechanical properties to those of polyethyleneare, on the other hand, aliphatic polyesters having a relatively highbiodegradation rate. They are advantageous in that molded products ofthem after use can be easily biodegraded or they easily compost. Theirbiodegradation rate is however not sufficiently high and a means forcontrolling their rate has not yet been developed.

Such polyesters are now produced by making use of polycondensation ofraw materials derived from fossil fuel resources. In view of concernsabout depletion of fossil fuel resources or an increase in carbondioxide in the air that poses a global-scale environmental problem inrecent years, methods for producing raw materials of these polymers frombiomass resources have attracted attentions. Since these resources arerenewable carbon-neutral biomasses, such methods are expected to gain inparticular importance in future.

There have heretofore been developed technologies for preparing adicarboxylic acid such as succinic acid or adipic acid from glucose,dextrose, cellulose, or oil or fat derived from biomass resources byusing the fermentation process (refer to Patent Document 1, Non-patentDocuments 1, 2 and 3).

These processes however provide a target dicarboxylic acid by preparingan organic acid salt of the dicarboxylic acid through fermentation andthen subjecting it to steps such as neutralization, extraction andcrystallization. Many impurities such as nitrogen elements derived fromfermentation microorganisms, ammonia and metal cations, as well asnitrogen elements contained in the biomass resources, are thereforemixed in the dicarboxylic acid inevitably.

There is also disclosed a production process of abiomass-resource-derived polyester (Patent Document 2).

-   Non-Patent Document: Expected Materials on the Future, Vol. 1, No.    11, p31 (2001)-   Patent Document 1: Japanese Patent Laid-Open No. 2005-27533-   Non-Patent Document 2: Biotechnology and Bioengineering Symp. No. 17    (1986), 355-363-   Non-Patent Document 3: Journal of the American Chemical Society No.    116 (1994), 399-400-   Non-Patent Document 4: Appl. Microbiol Biotechnol No. 51 (1999),    545-552-   Patent Document 2: Japanese Patent Laid-Open No. 2005-139287

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

The above-described biomass-resource-derived dicarboxylic acid or diolcontaining many impurities is typically used after subjected topurification treatment for reducing its impurity content. The presentinventors have found that even the dicarboxylic acid or diol subjectedto purification treatment contains nitrogen elements derived frommicroorganisms or enzymes, or nitrogen elements such as ammonia, sulfurelements, inorganic acids, organic acids and metal cations used in thepurification step, as well as nitrogen elements contained in the biomassresources, so that a polyester obtained using such a dicarboxylic acidcomponent and/or diol component derived from biomass resources as rawmaterials is not satisfactory in properties including hydrolysisresistance and therefore has difficulty in molding due to markedhydrolysis of the polymer during storage. It has been revealed by thestudy of the present inventors that the polyester disclosed in PatentDocument 2, on the other hand, is accompanied with the problem thatowing to a nitrogen content of the polyester as high as 44 ppm, thepolyester contains a large amount of terminal carboxylic acid groups sothat it lacks stability and it tends to generate foreign matters duringmolding.

An object of the present invention is therefore to provide, when adicarboxylic acid component and/or diol component derived from biomassresources are used as raw materials, a biomass-resource-derivedpolyester containing a specific amount of terminal acid groups andcapable of suppressing marked hydrolysis.

Means for Solving the Problems

The present inventors have carried out an extensive investigation with aview to overcoming the above-described problems. As a result, it hasbeen found that when a dicarboxylic acid and/or diol derived frombiomass resources are used as raw materials for a polyester, hydrolysisof the polyester due to water contained therein is acceleratedremarkably by the impurities contained in the raw materials and a markeddeterioration in mechanical properties of the polyester such as tensiletension occurs after storage. It has also been found that these problemscan be overcome by storing the polyester after reducing the amount of aspecific impurity therein to adjust the amount of a terminal acid groupin the polyester to 50 equivalents/metric ton or less, leading to thecompletion of the present invention.

The subject-matters of the present invention will next be described.

(1) A biomass-resource-derived polyester comprising as a main repeatingunit thereof a dicarboxylic acid unit and a diol unit, wherein at leastone of the dicarboxylic acid and diol used as raw materials of thepolyester is obtained from biomass resources and an amount of terminalacid in the polyester is 50 equivalents/metric ton or less.

(2) The biomass-resource-derived polyester as described above in (1),wherein the reduced viscosity (ηsp/c) of the polyester is 1.0 orgreater.

(3) The biomass-resource-derived polyester as described above in (1) or(2), wherein the water content in the polyester is, in terms of a massratio, 1 ppm or greater but not greater than 3000 ppm relative to thepolyester.

(4) The biomass-resource-derived polyester as described above in any oneof (1) to (3), wherein the YI value of the polyester is −10 or greaterbut not greater than 30.

(5) The biomass-resource-derived polyester as described above in any oneof (1) to (4), wherein a nitrogen atom content in the polyester exceptnitrogen atoms contained in the covalently bonded functional group inthe molecule of the polyester is, in terms of a mass ratio, 0.01 ppm orgreater but not greater than 1000 ppm relative to the polyester.

(6) The biomass-resource-derived polyester as described above in any oneof (1) to (5), wherein a sulfur atom content in the polyester is, interms of a mass ratio, 0.0001 ppm or greater but not greater than 50 ppmrelative to the polyester.

(7) The biomass-resource-derived polyester as described above in any oneof (1) to (6), which comprises at least one tri- or higher functionalcompound unit selected from the group consisting of tri- or higherfunctional polyhydric alcohols, tri- or higher functional polycarboxylicacids, and tri- or higher functional oxycarboxylic acids.

(8) The biomass-resource-derived polyester as described above in (7),wherein the content of the tri- or higher functional compound unit is0.0001 mole % or greater but not greater than 0.5 mole % based on 100mole % of all the monomer units constituting the polyester.

(9) The biomass-resource-derived polyester as described above in any oneof (1) to (8), wherein the dicarboxylic acid unit constituting the mainrepeating unit of the polyester is a biomass-resource-derived succinicacid unit.

(10) A process for producing a biomass-resource-derived polyester byreaction of a dicarboxylic acid and a diol, wherein at least one of thedicarboxylic acid as raw material and diol as raw material provided forthe reaction is derived from biomass resources; a nitrogen atom contentin the dicarboxylic acid as raw material and diol as raw material is, interms of a mass ratio, 0.01 ppm or greater but not greater than 2000 ppmrelative to the total amount of the raw materials; and the polyester hasan amount of terminal acid of 50 equivalents/metric ton or less.

(11) A process for producing a biomass-resource-derived polyester byreaction of a dicarboxylic acid and a diol, wherein at least one of thedicarboxylic acid as raw material and diol as raw material provided forthe reaction is derived from biomass resources; and a sulfur atomcontent in the dicarboxylic acid as raw material and diol as rawmaterial is, in terms of a mass ratio, 0.01 ppm or greater but notgreater than 100 ppm relative to the total amount of the raw materials.

(12) The process for producing a biomass-resource-derived polyester asdescribed above in (11), wherein the nitrogen atom content in thedicarboxylic acid as raw material and/or diol as raw material is, interms of a mass ratio, 0.01 ppm or greater but not greater than 2000 ppmrelative to the total amount of the raw materials.

(13) The process for producing a biomass-resource-derived polyester asdescribed above in any one of (10) to (12), wherein the reaction ispreformed in the presence of at least one tri- or higher functionalcompound selected from the group consisting of tri- or higher functionalpolyhydric alcohols, tri- or higher functional polycarboxylic acids andtri- or higher functional oxycarboxylic acids.

(14) A biomass-resource-derived polyester obtained by the process asdescribed above in any one of (10) to (13).

(15) A biomass-resource-derived polyester resin composition, whichcomprises 99.9 to 0.1 wt. % of a polyester as described above in any one(1) to (9) and (14) and 0.1 to 99.9 wt. % of a thermoplastic resin,biodegradable resin, natural resin or polysaccharide.

(16) A molded product obtained by molding a biomass-resource-derivedpolyester as described above in any one of (1) to (9) and (14).

(17) A molded product obtained by molding a polyester resin compositionas described above in (15).

(18) A pellet obtained from a biomass-resource-derived polyester asdescribed above in any one of (1) to (9) and (14).

Advantages of the Invention

The present invention makes it possible to provide, when a dicarboxylicacid and/or a diol derived from biomass resources is used as rawmaterials, a polyester capable of suppressing hydrolysis which willotherwise be accelerated by impurities contained therein and decreasingdeterioration in mechanical properties such as tensile elongation. Inaddition, development of this method contributes greatly to theresolution of environmental problems and depletion problems of fossilfuel resources, whereby resins having practically effective physicalproperties can be obtained. In particular, since a diol unit ordicarboxylic acid unit obtained from natural materials vegetated underthe earth's environment in the present atmosphere by the fermentationprocess or the like is used as a monomer of the polyester, raw materialsare available at a very low cost. The production areas of plant as rawmaterials are not limited but dispersed, which secures a very stablesupply of raw materials. In addition, the plant as raw materials areproduced under the earth's environment in the atmosphere so that arelatively good mass balance is achieved between absorption and releaseof carbon dioxide. Moreover, the polyester can be recognized as a veryeco-friendly and safe one. Such a polyester according to the presentinvention is not only excellent in physical properties, structure andfunction of the materials but also has a merit that it has a potentialpossibility of actualizing a recycling society which cannot be expectedfrom fossil-fuel-derived polyesters. The present invention provides apolyester production process which has a new perspective different fromthat of the conventional fossil-fuel-dependent polyester so that it willcontribute greatly to the utilization and growth of plastic materialsfrom an utterly new viewpoint that it is a new second-stage plastic. Thepolyester of the present invention emits neither harmful substance noroffensive odor even if disposal in soil is replaced by incineration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates the construction of pKMB1.

FIG. 2 schematically illustrates the construction of pKMB1/ΔLDH.

FIG. 3 schematically illustrates the construction of a pTZ vector.

FIG. 4 schematically illustrates the construction of pMJPC1.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will hereinafter be described specifically.

<Polyester>

The polyester which is a target of the present invention has adicarboxylic acid unit and a diol unit as essential components. In thepresent invention, at least either one of dicarboxylic acid or diolconstituting the dicarboxylic acid unit or diol unit, respectively, ispreferably derived from biomass resources.

Dicarboxylic Acid Unit

Examples of the dicarboxylic acid constituting the dicarboxylic acidunit include aliphatic dicarboxylic acids or mixtures thereof, aromaticdicarboxylic acids or mixtures thereof, and mixtures of aromaticdicarboxylic acid and aliphatic dicarboxylic acid. Of these,dicarboxylic acids having, as a main component thereof, an aliphaticdicarboxylic acid are preferred. The term “main component” as usedherein means that the component is contained in an amount of typically50 mole % or greater, preferably 60 mole % or greater, more preferably70 mole % or greater, especially preferably 90 mole % or greater basedon the whole dicarboxylic acid unit.

Examples of the aromatic dicarboxylic acids include terephthalic acidand isophthalic acid. Examples of the derivatives of the aromaticdicarboxylic acid include lower alkyl esters of an aromatic dicarboxylicacid, more specifically, methyl ester, ethyl ester, propyl ester andbutyl ester of an aromatic dicarboxylic acid. Of these, terephthalicacid is preferred as the aromatic dicarboxylic acid and dimethylterephthalate is preferred as the derivative of an aromatic dicarboxylicacid. Even when an aromatic dicarboxylic acid as disclosed herein isused, a desired aromatic polyester, for example, a polyester of dimethylterephthalate and 1,4-butanediol is available by using an arbitraryaromatic dicarboxylic acid.

As the aliphatic dicarboxylic acid, aliphatic dicarboxylic acids orderivatives thereof are used. Specific examples of the aliphaticdicarboxylic acid include linear or alicyclic dicarboxylic acids havingtypically 2 or greater but not greater than 40 carbon atoms such asoxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid,dodecanedioic acid, dimer acid and cyclohexanedicarboxylic acid. As thederivative of the aliphatic dicarboxylic acid, lower alkyl esters of thealiphatic dicarboxylic acid such as methyl ester, ethyl ester, propylester and butyl ester of the aliphatic dicarboxylic acid and cyclic acidanhydrides of the aliphatic dicarboxylic acid such as succinic anhydrideare usable. Of these, adipic acid, succinic acid, and dimer acid andmixtures thereof are preferred as the aliphatic dicarboxylic acid fromthe viewpoint of the physical properties of the polymer thus available,with the aliphatic dicarboxylic acids having succinic acid as a maincomponent being especially preferred. As the derivative of the aliphaticdicarboxylic acid, methyl adipate and methyl succinate, and mixturethereof are more preferred.

These dicarboxylic acids may be used either singly or as a mixture oftwo or more thereof.

In the present invention, these dicarboxylic acids are preferablyderived from biomass resources.

The term “biomass resources” as used herein embraces resources in whichthe energy of sunlight has been stored in the form of starches orcelluloses by the photosynthesis of plants; animal bodies which havegrown by eating plant bodies; and products available by processing theplant bodies or animal bodies. Of these, plant resources are morepreferred as biomass resources. Examples include wood, paddy straws,rice husks, rice bran, long-stored rice, corn, sugarcanes, cassava, sagopalms, bean curd refuses, corn cobs, tapioca wastes, bagasse, plant oilwastes, potatoes, buckwheats, soybeans, oils or fats, used paper,residues after paper manufacture, residues of marine products, livestockexcrement, sewage sludge and leftover food. Of these, wood, paddystraws, rice husks, rice bran, long-stored rice, corn, sugarcanes,cassava, sago palms, bean curd refuses, corn cobs, tapioca wastes,bagasse, plant oil wastes, potatoes, buckwheats, soybeans, oils or fats,used paper, and residues after paper manufacture are preferred, withwood, paddy straws, rice husks, long-stored rice, corn, sugarcanes,cassava, sago palms, potatoes, oils or fats, used paper, and residuesafter paper manufacture being more preferred. Corn, sugarcanes, cassavaand sago palms are most preferred. These biomass resources typicallycontain a nitrogen element, and many alkali metals and alkaline earthmetals such as Na, K, Mg and Ca.

These biomass resources are transformed into carbon sources after, notparticularly limited to, known pretreatment and glycosylation steps suchas chemical treatment with acids or alkalis, biological treatment withmicroorganisms and physical treatment. This step typically includes, butnot particularly limited to, a miniaturization step by pretreatment tomake biomass resources into chips, or shave or grind them. It includesif necessary a pulverization step in a grinder or mill. The biomassresources thus miniaturized are converted into carbon sources after thepretreatment and glycosylation steps. Specific examples of thepretreatment and glycosylation methods include chemical methods such astreatment with a strong acid such as sulfuric acid, nitric acid,hydrochloric acid or phosphoric acid, alkali treatment, ammonia freezeexplosion treatment, solvent extraction, supercritical fluid treatmentand treatment with an oxidizing agent; physical methods such as finegrinding, steam explosion treatment, treatment with microwaves andexposure to electron beam; and biological treatment such as hydrolysiswith microorganisms or enzymatic treatment.

As the carbon sources derived from the above-described biomassresources, typically used are fermentable carbohydrates such as hexosessuch as glucose, mannose, galactose, fructose, sorbose and tagatose;pentoses such as arabinose, xylose, ribose, xylulose and ribulose;disaccharides and polysaccharides such as pentosan, saccharose, starchand cellulose; oils or fats such as butyric acid, caproic acid, caprylicacid, capric acid, lauric acid, myristic acid, palmitic acid,palmitoleic acid, stearic acid, oleic acid, linoleic acid, linolenicacid, monocutinic acid, arachic acid, eicosenoic acid, arachidonic acid,behenic acid, erucic acid, docosapentaenoic acid, docosahexaenoic acid,lignoceric acid, and ceracoreic acid; and polyalcohols such as glycerin,mannitol, xylitol and ribitol. Of these, glucose, fructose and xyloseare preferred, with glucose being especially preferred. As carbonsources derived from plant resources in a broad sense, celluloses, amain component of paper, are preferred.

A dicarboxylic acid is synthesized using the above-described carbonsources in accordance with the fermentation process utilizing microbialconversion, a chemical conversion process including a reaction step suchas hydrolysis, dehydration, hydration or oxidation, or a combination ofthe fermentation process and chemical conversion process. Of these, thefermentation process utilizing microbial conversion is preferred.

No particular limitation is imposed on the microorganism used formicrobial conversion insofar as it has a producing capacity of adicarboxylic acid. Examples of the microorganism include anaerobicbacteria such as those belonging to the genus Anaerobiospirillum (U.S.Pat. No. 5,143,833), facultative anaerobic bacteria (E. coli (J.Bacteriol., 57: 147-158) such as those belonging to the genusActinobacillus (U.S. Pat. No. 5,504,004) and the genus Escherichia (U.S.Pat. No. 5,770,435), or E. coli mutant (International Patent PublicationNo. 2000-500333, U.S. Pat. No. 6,159,738 or the like), aerobic bacteriasuch as those belonging to the genus Corynebacterium (Japanese PatentLaid-Open No. Hei 11-113588), aerobic bacteria (Japanese PatentLaid-Open No. 2003-235593) such as those belonging to the genusBacillus, genus Rizobium, genus Brevibacterium or genus Arthrobacter,and anaerobic rumen bacteria such as Bacteroidesruminicola andBacteroidesamylophilus. The above-described references are incorporatedherein by reference.

More specifically, as the parent strain of the bacteria usable in thepresent invention, coryneform bacteria, bacillus bacteria and rhizobiumbacteria are preferred, with coryneform bacteria being more preferred.These bacteria have a producing capacity of succinic acid by making useof microbial conversion.

Examples of the coryneform bacteria include microorganisms belonging tothe genus Corynebacterium, microorganisms belonging to the genusBrevibacterium and microorganisms belonging to the genus Arthrobacter,with those belonging to the genus Corynebacterium and those belonging tothe genus Brevibacterium being preferred. More preferred aremicroorganisms belonging to Corynebacterium glutamicum, Brevibacteriumflavum, Brevibacterium ammoniagenes and Brevibacterium lactofermentum.

Especially preferred specific examples of the parent strain of theabove-described bacteria include Brevibacterium flavum MJ-233 (FERMBP-1497), Brevibacterium flavum MJ-233 AB-41 (FERM BP-1498),Brevibacterium ammoniagenes ATCC6872, Corynebacterium glutamicumATCC31831, and Brevibacterium lactofermentum ATCC13869. SinceBrevibacterium flavum is sometimes classified as Corynebacteriumglutamicum (Lielbl, W., Ehrmann, M., Ludwig, W. and Schleifer, K. H.,International Journal of Systematic Bacteriology, 1991, vol. 41,p255-260), Brevibacterium flavum MJ-233 strain and its mutant MJ-233AB-41 strain are regarded in the present invention to be equal toCorynebacterium glutamicum MJ-233 strain and MJ-233 AB-41 strain,respectively.

Brevibacterium flavum MJ-233 was deposited as accession number FERMP-3068, on Apr. 28, 1975, with the National Institute of Bioscience andHuman-Technology, Agency of Industrial Science and Technology, Ministryof International Trade and Industry (present Patent MicroorganismDepositary Center, National Institute of Advanced Industrial Science andTechnology) (Center 6, 1-1, Higashi 1-chome, Tsukuba-shi, Ibaraki-ken,305-8566 Japan) and was transferred to international deposition underthe Budapest Treaty on May 1, 1981, and Deposit No. FERM BP-1497 wasallotted thereto.

Brevibacterium flavum MJ-233-AB-41 was deposited as accession numberFERM P-3812, on Nov. 17, 1976, with the National Institute of Bioscienceand Human-Technology, Agency of Industrial Science and Technology,Ministry of International Trade and Industry (present PatentMicroorganism Depositary Center, National Institute of AdvancedIndustrial Science and Technology (Center 6, 1-1, Higashi 1-chome,Tsukuba-shi, Ibaraki-ken, 305-8566 Japan), and was transferred tointernational deposition under the Budapest Treaty on May 1, 1981, andDeposit No. FERM BP-1498 was allotted thereto.

Reaction conditions in the microbial conversion such as reactiontemperature and pressure are determined, depending on the activity ofmicroorganisms such as bacteria and fungi selected. Suitable conditionsfor obtaining a dicarboxylic acid may be selected as needed.

In the microbial conversion, a decrease in pH may deteriorate metabolicactivity of microorganisms or stop the activity of microorganisms, whichresults in reduction in production yield or death of the microorganisms.Usually, a neutralizing agent is therefore employed. The pH in thereaction system is usually measured using a pH sensor and it is adjustedto fall within a predetermined pH range by the addition of theneutralizing agent. No particular limitation is imposed on the addingmethod of the neutralizing agent and it may be continuous addition orintermittent addition.

Examples of the neutralizing agent include ammonia, ammonium carbonate,urea, hydroxides of an alkali metal, hydroxides of an alkaline earthmetal, carbonates of an alkali metal, and carbonates of an alkalineearth metal. Of these, ammonia, ammonium carbonate and urea arepreferred. The hydroxides of an alkali (alkaline earth) metal includeNaOH, KOH, Ca(OH)₂, and Mg(OH)₂ and mixtures thereof, while thecarbonates of an alkali (alkaline earth) metal include Na₂CO₃, K₂CO₃,CaCO₃, MgrCO₃, and NaKCO₃ and mixtures thereof.

The pH is adjusted to fall within a range in which each of themicroorganisms such as bacteria and fungi can exhibit its activity mosteffectively. It is typically from pH 4 to 10, preferably from about 6 to9.

As a method of purifying a dicarboxylic acid obtained by a productionprocess including the fermentation process, there has been known amethod using electrodialysis, a method using an ion exchange resin, anda salt exchange method. For example, a dicarboxylic acid may be purifiedusing both electrodialysis and a water splitting step in combination forseparating a dicarboxylate and thereby preparing a pure acid, followedby further purification by passing a product stream through a series ofion exchange columns or by using water splitting electrodialysis toconvert into a supersaturated solution of a dicarboxylic acid (U.S. Pat.No. 5,034,105). As the salt exchange method, a dicarboxylic acid may bepurified, for example, by mixing an ammonia salt of a dicarboxylic acidwith ammonium hydrogen sulfate and/or sulfuric acid at a sufficientlylow pH and causing a reaction between them to produce the correspondingdicarboxylic acid and ammonium sulfate (International Patent PublicationNo. 2001-514900). Specific methods using an ion exchange resin include amethod of removing a solid content such as fungus body from adicarboxylic acid solution by centrifugal separation, filtration or thelike, desalting the resulting solution through an ion exchange resin,and separating and purifying the dicarboxylic acid from the solution bycrystallization or column chromatography. Further purification methodsinclude a method, as described in Japanese Patent Laid-Open No. Hei3-30685, of carrying out fermentation while using calcium hydroxide as aneutralizing agent, removing a calcium sulfate precipitate formed by theaddition of sulfuric acid, and then treating the residue with a strongacidic ion exchange resin and a weakly basic ion exchange resin; and amethod, as described in Japanese Patent Laid-Open No. Hei 2-283289, ofsubjecting a succinate formed by the fermentation process toelectrodialysis and then treating the product with a strongly acidic ionexchange resin and weakly basic ion exchange resin. Methods described inU.S. Pat. No. 6,284,904 and Japanese Patent Laid-Open No. 2004-196768are also preferred. In the present invention, any purification methodmay be used. A purified monomer as raw material suited for the presentinvention can be obtained by using, in any combination and if necessaryin repetition, desired unit operations selected from those described inthe above-described known literatures or Referential Examples of thepresent invention, for example, a method using electrodialysis, a methodusing an ion exchange resin, a method treating with an acid such assulfuric acid, crystallization using water, alcohol, carboxylic acid ormixture thereof, washing, filtration and drying. Of these, an ionexchange method or salt exchange method is preferred from the viewpointsof cost and efficiency, of which the salt exchange method is especiallypreferred from the viewpoint of industrial productivity.

It is usually necessary to reduce the amount of impurities such asnitrogen compound and metal cation contained in the dicarboxylic acid bypurification, thereby obtaining a practical polymer.

The dicarboxylic acid derived from biomass resources by theabove-described process inevitably contains a nitrogen atom as animpurity. They are impurities from biomass resources themselves andthose resulting from fermentation treatment and purification treatmentincluding neutralization with an acid. More specifically, nitrogen atomsderived from amino acids, proteins, ammonium salts, urea, andfermentation microorganisms are contained in the dicarboxylic acid.

With regard to the nitrogen atom content in the dicarboxylic acidderived from the biomass resources by the above-described process, theupper limit is typically 2000 ppm or less, preferably 1000 ppm or less,more preferably 100 ppm or less, most preferably 50 ppm or less based onthe mass of the dicarboxylic acid. The lower limit is typically 0.01 ppmor greater, preferably 0.05 ppm or greater. From the economical reasonin the purification step, it is more preferably 0.1 ppm or greater, morepreferably 1 ppm or greater, especially preferably 10 ppm or greater.Excessively great nitrogen atom contents tend to cause retardation of apolymerization reaction, an increase in the number of terminal carboxylgroups of the polymer thus produced, coloration, partial gelation anddeterioration in stability. Although too low nitrogen atom contents arepreferred, they are not advantageous economically because they may makethe purification step complicated.

The nitrogen atom content is a value as measured by a known method suchas elemental analysis or a method of separating an amino acid andammonia from a sample under biogenic amino acid separating conditionsand detecting it by ninhydrin colorimetry.

Use of the dicarboxylic acid having a nitrogen atom content fallingwithin the above-described range is advantageous in reducing colorationof a polyester thus obtained. It is also effective for suppressingretardation of the polymerization reaction of the polyester.

Examples of a specific method for efficiently reducing the amount ofammonia contained as an impurity in the dicarboxylic acid include areaction crystallization method using a weakly acidic organic acidhaving a higher pH than that of the target dicarboxylic acid.

When the dicarboxylic acid prepared by the fermentation process is used,it may contain a sulfur atom originating from the purification treatmentincluding a neutralization step with an acid. Specific examples of thesulfur-atom-containing impurity include sulfuric acid, sulfates,sulfurous acid, organic sulfonic acids and organic sulfonates.

With regard to the sulfur atom content in the dicarboxylic acid, theupper limit is typically 100 ppm or less, preferably 20 ppm or less,more preferably 10 ppm or less, especially preferably 5 ppm or less,most preferably 0.5 ppm or less based on the mass of the dicarboxylicacid. The lower limit of it is, on the other hand, typically 0.001 ppmor greater, preferably 0.01 ppm or greater, more preferably 0.05 ppm orgreater, especially preferably 0.1 ppm or greater. Excessively greatsulfur atom contents tend to cause retardation of a polymerizationreaction, partial gelation of the resulting polymer, an increase in thenumber of terminal carboxyl groups of the resulting polymer, anddeterioration in stability. Although too low sulfur atom contents arepreferred, they are not advantageous economically because they may makethe purification step complicated. The sulfur atom content is a value asmeasured by known elemental analysis.

In the invention, when the biomass-resource-derived dicarboxylic acidobtained by the above-described process is used as a raw material forpolyester, the oxygen concentration in a storage tank of thedicarboxylic acid to be connected to a polymerization system may becontrolled to a predetermined value or less. By this control, colorationof the polyester, which will otherwise occur due to the oxidationreaction of nitrogen sources contained as an impurity, can be prevented.

A tank is typically employed for storing raw materials while controllingthe oxygen concentration, but an apparatus other than a tank is alsousable without particular limitation insofar as it can control theoxygen concentration. No specific limitation is imposed on the kind ofthe storage tank and known ones such as metal containers, metalcontainers having a glass or resin-lined inside, or containers made ofglass or resin are usable. From the standpoint of strength, storagetanks made of a metal or those having a glass or resin lined inside arepreferred. For the tank made of a metal, known materials are used.Specific examples include carbon steel, ferrite steel, martensiticstainless steels such as SUS 410, austenitic stainless steels such asSUS310, SUS304 and SUS316, clad steel, cast: iron, copper, copper alloy,aluminum, inconel, hastelloy and titanium.

Although no particular limitation is imposed on the lower limit of theoxygen concentration in the storage tank of the dicarboxylic acid basedon the total volume of the storage tank, it is typically 0.00001% orgreater, preferably 0.01% or greater. The upper limit is on the otherhand, 16% or less, preferably 14% or less, more preferably 12% or less.Too low oxygen concentrations are economically disadvantageous becausethey may make the equipment or control step complicated. Too high oxygenconcentrations, on the other hand, tend to enhance the coloration of apolymer thus prepared.

With regard to the temperature of the dicarboxylic acid in the storagetank, the lower limit is typically −50° C. or greater, preferably 0° C.or greater. The upper limit is, on the other hand, typically 200° C. orless, preferably 100° C. or less, more preferably 50° C. or less.Storage at room temperature is most preferred because it does not needany temperature control. Too low temperatures tend to increase thestorage cost, while too high temperatures tend to cause dehydrationreaction or the like of the dicarboxylic acid simultaneously.

Although no particular limitation is imposed on the lower limit of thehumidity in the storage tank of the dicarboxylic acid based on the totalvolume of the storage tank, it is typically 0.0001% or greater,preferably 0.001% or greater, more preferably 0.01% or greater, mostpreferably 0.1% or greater. The upper limit is 80% or less, preferably60% or less, more preferably 40% or less. Too low humidities tend to beeconomically disadvantageous because the humidity control step becomestoo complicated. Too high humidities tend to cause problems such asattachment of the dicarboxylic acid to the storage tank or pipes,blocking of the dicarboxylic acid and, if the storage tank is made of ametal, corrosion of the tank.

The pressure in the storage tank of the dicarboxylic acid is typicallyatmospheric pressure (normal pressure).

The dicarboxylic acid to be used in the present invention is preferablyless colored typically. The upper limit of the yellowness (YI) of thedicarboxylic acid to be used in the present invention is typically 50 orless, preferably 20 or less, more preferably 10 or less, still morepreferably 6 or less, especially preferably 4 or less. Although noparticular limitation is imposed on the lower limit, it is typically −20or greater, preferably −10 or greater, more preferably −5 or greater,especially preferably −3 or greater, most preferably −1 or greater. Thepolymer available from the dicarboxylic acid having a high YI has thedrawback that it is highly colored. The dicarboxylic acid having a lowYI is preferred, but use of it is economically disadvantageous becauseit needs a lot of time for its preparation as well as expensiveequipment investment. In the present invention, the YI is a valuedetermined by the measurement based on JIS K7105.

(2) Diol Unit

The term “diol unit” as used herein means a unit derived from aromaticdiols and/or aliphatic diols. Known diol compounds are usable as them,but aliphatic diols are preferred.

Although no particular limitation is imposed on the aliphatic diolinsofar as it is an aliphatic or alicyclic compound having two OHgroups, examples of it include aliphatic diols having carbon atoms, asthe lower limit thereof, of 2 or greater and, as the upper limit, oftypically 10 or less, preferably 6 or less. Of these, diols having aneven number of carbon atoms and mixtures thereof are preferred becausepolymers having a higher melting point are available from them.

Specific examples of the aliphatic diol include ethylene glycol,1,3-propylene glycol, neopentyl glycol, 1,6-hexamethylene glycol,decamethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol.These may be used either singly or as a mixture of two or more of them.

Of these, ethylene glycol, 1,4-butanediol, 1,3-propylene glycol, and1,4-cyclohexanedimethanol are preferred, of which ethylene glycol and1,4-butanediol, and mixtures thereof are preferred. Furthermore,aliphatic diols having 1,4-butanediol as a main component thereof aremore preferred, with 1,4-butanediol being especially preferred. The term“main component” as used herein means that it is contained in an amountof typically 50 mole % or greater, preferably 60 mole % or greater, morepreferably 70 mole % or greater, especially preferably 90 mole % orgreater based on all the diol units.

Although no particular limitation is imposed on the aromatic diolinsofar as it is an aromatic compound having two OH groups, examples ofit include aromatic diols having 6 or greater carbon atoms as a lowerlimit and 15 or less carbon atoms as an upper limit. Specific examplesof it include hydroquinone, 1,5-dihydroxynaphthalene,4,4′-dihydroxydiphenyl, bis(p-hydroxyphenyl)methane andbis(p-hydroxyphenyl)-2,2-propane. The content of the aromatic diol inthe total amount of all the diols is typically 30 mole % or less,preferably 20 mole % or less, more preferably 10 mole % or less.

Furthermore, a both-hydroxy-terminated polyether (polyether having ahydroxyl at both terminals) may be used in combination with theabove-described aliphatic diol. With regard to the number of carbonatoms of the both-hydroxy-terminated polyether, the lower limit istypically 4 or greater, preferably 10 or greater, while the upper limitis typically 1000 or less, preferably 200 or less, more preferably 100or less.

Specific examples of the both-hydroxy-terminated polyether includediethylene glycol, triethylene glycol, polyethylene glycol,polypropylene glycol, polytetramethylene glycol, poly-1,3-propanedioland poly-1,6-hexamethylene glycol. Moreover, copolymer polyether betweenpolyethylene glycol and polypropylene glycol, and the like can be alsoused. The using amount of the both-hydroxy-terminated polyether istypically 90 wt. % or less, preferably 50 wt. % or less, more preferably30 wt. % or less in terms of a calculated content in the polyester.

In the present invention, these diols may be derived from biomassresources. More specifically, the diol compound may be prepared directlyfrom carbon sources such as glucose by the fermentation process or itmay be prepared by the conversion of a dicarboxylic acid, dicarboxylicanhydride or cyclic ether, which has been obtained by the fermentationprocess, by a chemical reaction.

For example, 1,4-butanediol may be prepared by a chemical reaction ofsuccinic acid, succinic anhydride, succinate ester, maleic acid, maleicanhydride, maleate ester, tetrahydrofuran or γ-butyrolactone, or it maybe prepared from 1,3-butadiene obtained by the fermentation process. Ofthese, a method of obtaining 1,4-butanediol by the hydrogenation ofsuccinic acid in the presence of a reduction catalyst is efficient andis therefore preferred.

Examples of the catalyst to be used for hydrogenation of succinic acidinclude Pd, Ru, Re, Rh, Ni, Cu, and Co, and compounds thereof. Specificexamples of it include Pd/Ag/Re, Ru/Ni/Co/ZnO, Cu/Zn oxide, Cu/Zn/Croxide, Ru/Re, Re/C, Ru/Sn, Ru/Pt/Sn, Pt/Re/alkali, Pt/Re, Pd/Co/Re,Cu/Si, Cu/Cr/Mn, ReO/CuO/ZnO, CuO/CrO, Pd/Re, Ni/Co, Pd/CuO/CrO₃,phosphoric acid-Ru, Ni/Co, Co/Ru/Mn, Cu/Pd/KOH and Cu/Cr/Zn. Of these,Ru/Sn and Ru/Pt/Sn are preferred because of their catalytic activity.

A process of preparing a diol compound from biomass resources by usingknown organic chemical catalytic reactions in combination is also usedpreferably. For example, when pentose is used as a biomass resource, adiol such as butane diol can easily be prepared by using knowndehydration reaction and catalytic reaction in combination.

The diol derived from biomass resources sometimes contains a nitrogenatom as an impurity originating from the biomass resources themselves,fermentation treatment or purification treatment including aneutralization step with an acid. In this case, specifically, itcontains a nitrogen atom derived from amino acids, proteins, ammonia,urea, and fermentation microorganisms.

With regard to the nitrogen atom content in the diol prepared by thefermentation process, the upper limit is typically 2000 ppm or less,preferably 1000 ppm or less, more preferably 100 ppm or less, mostpreferably 50 ppm or less based on the mass of the diol. Although noparticular limitation is imposed on the lower limit, it is typically0.01 ppm or greater, preferably 0.05 ppm or greater. From the viewpointof the economy of the purification step, it is more preferably 0.1 ppmor greater, still more preferably 1 ppm or greater, especiallypreferably 10 ppm or greater. Excessively high contents tend to causeretardation of a polymerization reaction and an increase in the numberof terminal carboxyl groups, coloration, partial gelation anddeterioration in stability of the resulting polymer. Excessively lowcontents, on the other hand, are economically disadvantageous becausethey may make the purification step complicated.

In another mode, the upper limit of the nitrogen atom content in thedicarboxylic acid as raw material and diol is typically 2000 ppm orless, preferably 1000 ppm or less, more preferably 100 ppm or less, mostpreferably 50 ppm or less based on the total mass of the above-describedraw materials. Although no particular limitation is imposed on the lowerlimit, it is typically 0.01 ppm or greater, preferably 0.05 ppm orgreater, 0.1 ppm or greater.

When the diol prepared by the fermentation process is used, it maycontain a sulfur atom originating from the purification treatmentincluding neutralization step with an acid. Specific examples of thesulfur-containing impurity include sulfuric acid, sulfurous acid, andorganic sulfonates.

With regard to the sulfur atom content in the diol, the upper limit istypically 100 ppm or less, preferably 20 ppm or less, more preferably 10ppm or less, especially preferably 5 ppm or less, most preferably 0.5ppm or less based on the mass of the diol. Although no particularlimitation is imposed on the lower limit, it is typically 0.001 ppm orgreater, preferably 0.01 ppm or greater, more preferably 0.05 ppm orgreater, especially preferably 0.1 ppm or greater. Excessively greatsulfur atom contents tend to cause retardation of a polymerizationreaction and partial gelation, increase in the number of terminalcarboxyl groups, and stability deterioration of the resulting polymer.Although too low sulfur atom contents are preferred, they are notadvantageous economically because they may make the purification stepcomplicated. The sulfur atom content is a value as measured by knownelemental analysis.

In another mode, the upper limit of the sulfur atom content in thedicarboxylic acid as raw material and diol is, in terms of atoms,typically 100 ppm or less, preferably 20 ppm or less, more preferably 10ppm or less, especially preferably 5 ppm or less, most preferably 0.5ppm or less based on the total mass of the raw materials. Although noparticular limitation is imposed on the lower limit, it is typically0.001 ppm or greater, preferably 0.01 ppm or greater, more preferably0.05 ppm or greater, especially preferably 0.1 ppm or greater.

In the present invention, when the biomass-resource-derived diolobtained by the above-described process is used as a raw material of apolyester, the oxygen concentration or temperature in a storage tank ofthe diol connected to a polymerization system may be controlled in orderto suppress coloration of the polyester which will otherwise occur bythe impurity. This control makes it possible to suppress the colorationof the impurity itself or oxidation reaction of the diol accelerated bythe impurity. For example, when 1,4-butanediol is employed, colorationof a polyester due to an oxidation product of the diol such as2-(4-hydroxybutyloxy)tetrahydrofuran can be prevented.

A tank is typically employed for storing raw materials while controllingthe oxygen concentration, but any apparatus is usable without particularlimitation insofar as it can control the oxygen concentration. Nospecific limitation is imposed on the kind of the storage tank and knownones such as those made of a metal, those made of a metal having a glassor resin-lined inside, or containers made of glass or resin are usable.From the standpoint of strength, storage tanks made of a metal or thosehaving a glass or resin-lined inside are preferred. For the tanks madeof a metal, known materials are used. Specific examples include carbonsteel, ferrite steel, martensitic stainless steels such as SUS410,austenitic stainless steels such as SUS310, SUS304 and SUS316, cladsteel, cast iron, copper, copper alloy, aluminum, inconel, hastelloy andtitanium.

Although no particular limitation is imposed on the lower limit of theoxygen concentration in the storage tank of the diol based on the totalvolume of the storage tank, but it is typically 0.00001% or greater,preferably 0.0001% or greater, more preferably 0.001% or greater, mostpreferably 0.01% or greater. The upper limit is typically 10% or less,preferably 5% or less, more preferably 1% or less, most preferably 0.1%or less. Too low oxygen concentrations are economically disadvantageousbecause they may make the control step complicated. Too high oxygenconcentrations, on the other hand, tend to enhance the coloration of theresulting polymer due to the oxidation reaction product of the diol.

The lower limit of the storage temperature in the storage tank of thediol is typically 15° C. or greater, preferably 30° C. or greater, morepreferably 50° C. or greater, most preferably 100° C. or greater. Theupper limit is 230° C. or less, preferably 200° C. or less, morepreferably 180° C. or less, most preferably 160° C. or less. Too lowtemperatures are economically disadvantageous for polyester manufacturebecause it tends to take much time to raise the temperature at the timeof polyester production and in addition, the diol sometimes solidifies.Too high temperatures, on the other hand, are not only economicallydisadvantageous because of necessity of high-pressure storage equipmentbut also tend to enhance deterioration of the diol.

The pressure in the storage tank of the diol is typically atmosphericpressure (normal pressure). Too high or too low pressures areeconomically disadvantageous because they make controlling equipmentcomplicated.

In the present invention, the upper limit of the content, in the diol,of the oxidation product of the diol to be used for the production of apolymer having a good hue is typically 10000 ppm or less, preferably5000 ppm or less, more preferably 3000 ppm or less, most preferably 2000ppm or less. Although no particular limitation is imposed on the lowerlimit, it is typically 1 ppm or greater. Owing to economic reasons ofthe purification step, it is preferably 10 ppm or greater, morepreferably 100 ppm or greater.

In the present invention, the diol is typically used as a raw materialof a polyester after a purification step by distillation.

In the present invention, any polyesters produced by a reaction ofcomponents composed mainly of various compounds belonging to theabove-described respective ranges of the dicarboxylic acid unit and diolunit are embraced in the polyester of the present invention. Followingpolyesters can be exemplified specifically as typical examples. Examplesof the polyester produced using succinic acid include polyester composedof succinic acid and ethylene glycol, polyester composed of succinicacid and 1,3-propylene glycol, polyester composed of succinic acid andneopentyl glycol, polyester composed of succinic acid and1,6-hexamethylene glycol, polyester composed of succinic acid and1,4-butanediol, and polyester composed of succinic acid and1,4-cyclohexanedimethanol.

Examples of the polyester produced using oxalic acid include polyestercomposed of oxalic acid and ethylene glycol, polyester composed ofoxalic acid and 1,3-propylene glycol, polyester composed of oxalic acidand neopentyl glycol, polyester composed of oxalic acid and1,6-hexamethylene glycol, polyester composed of oxalic acid and1,4-butanediol, and polyester composed of oxalic acid and1,4-cyclohexanedimethanol.

Examples of the polyester produced using adipic acid include polyestercomposed of adipic acid and ethylene glycol, polyester composed ofadipic acid and 1,3-propylene glycol, polyester composed of adipic acidand neopentyl glycol, polyester composed of adipic acid and1,6-hexamethylene glycol, polyester composed of adipic acid and1,4-butanediol, and polyester composed of adipic acid and1,4-cyclohexanedimethanol.

Polyesters obtained using the above-described dicarboxylic acid incombination are also preferred. Examples include polyester composed ofsuccinic acid, adipic acid and ethylene glycol, polyester composed ofsuccinic acid, adipic acid and 1,4-butanediol, polyester composed ofterephthalic acid, adipic acid and 1,4-butanediol and polyester composedof terephthalic acid, succinic acid and 1,4-butanediol.

The present invention also embraces a copolymer polyester composed of,in addition to the diol component and dicarboxylic acid component, acopolymerizable component as a third component. As specific examples ofthe copolymerizable component, at least one polyfunctional compoundselected from the group consisting of bifunctional oxycarboxylic acidsand tri- or higher functional polyhydric alcohols, tri- or higherfunctional polycarboxylic acids and/or anhydrides thereof, and tri- orhigher functional oxycarboxylic acids for forming a crosslinkedstructure. Of these copolymerizable components, bifunctional and/or tri-or higher functional oxycarboxylic acids are especially preferredbecause they facilitate preparation of a copolyester having a highdegree of polymerization. Above all, use of a tri- or higher functionaloxycarboxylic acid is most preferred because even a very small amount ofit facilitates production of a polyester having a high degree ofpolymerization without using a chain extender which will be describedlater.

Specific examples of the bifunctional oxycarboxylic acid include lacticacid, glycolic acid, hydroxybutyric acid, hydroxycaproic acid,2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid,2-hydroxyisocaproic acid, and caprolactone. They may be derivatives ofan oxycarboxylic acid such as esters or lactones of the oxycarboxylicacid and polymers of the oxycarboxylic acid. Moreover, theseoxycarboxylic acids may be used either singly or as mixtures of two ormore thereof. In the case where they have optical isomers, the opticalisomers may be any of D-form, L-form, or racemic-form and they may be inthe form of a solid, liquid, or aqueous solution. Of these, easilyavailable lactic acid or glycolic acid is especially preferred. Lacticacid or glycolic acid in the form of a 30 to 95% aqueous solution ispreferred because it is easily available. When a bifunctionaloxycarboxylic acid is used as a copolymerizable component in order toproduce a polyester having a high degree of polymerization, a desiredcopolyester can be obtained by the addition of any bifunctionaloxycarboxylic acid during polymerization. The lower limit of the usingamount at which it exhibits its effect is typically 0.02 mole % orgreater, preferably 0.5 mole % or greater, more preferably 1.0 mole % orgreater based on the raw material monomer. The upper limit of the usingamount is, on the other hand, typically 30 mole % or less, preferably 20mole % or less, more preferably 10 mole % or less.

Specific modes of the polyester include, when lactic acid is used as thebifunctional oxycarboxylic acid, a succinic acid-1,4-butanediol-lacticacid copolyester and a succinic acid-adipic acid-1,4-butanediol-lacticacid copolyester; and when glycolic acid is used, a succinicacid-1,4-butanediol-glycolic acid copolyester.

Specific examples of the tri- or higher functional polyhydric alcoholinclude glycerin, trimethylolpropane and pentaerythritol. They may beused either singly or as a mixture of two or more thereof.

When pentaerythritol is used as the tri- or higher functional polyhydricalcohol as the copolymerizable component, a succinicacid-1,4-butanediol-pentaerythritol copolyester or a succinicacid-adipic acid-1,4-butanediol-pentaerythritol copolyester can beobtained. A desired copolyester can be produced by changing the tri- orhigher functional polyhydric alcohol as needed. High molecular weightpolyesters obtained by chain extension (coupling) of these copolyestersare also embraced in the polyester of the present invention.

Specific examples of the tri- or higher functional polycarboxylic acidor anhydride thereof include propanetricarboxylic acid, pyromelliticanhydride, benzophenonetetracarboxylic anhydride, andcyclopentatetracarboxylic anhydride. They may be used either singly oras a mixture of two or more thereof.

Specific examples of the tri- or higher functional oxycarboxylic acidinclude malic acid, hydroxyglutaric acid, hydroxymethylglutaric acid,tartaric acid, citric acid, hydroxyisophthalic acid, andhydroxyterephthalic acid. They may be used either singly or as a mixtureof two or more thereof. Of these, malic acid, tartaric acid, and citricacid, and mixtures thereof are especially preferred because of easyavailability. When malic acid is used as a trifunctional oxycarboxylicacid serving as the copolymerizable component, examples of thecopolyester thus available include succinic acid-1,4-butanediol-malicacid copolyester, succinic acid-adipic acid-1,4-butanediol-malic acidcopolyester, succinic acid-1,4-butanediol-malic acid-tartaric acidcopolyester, succinic acid-adipic acid-1,4-butanediol-malicacid-tartaric acid copolyester, succinic acid-1,4-butanediol-malicacid-citric acid copolyester, and succinic acid-adipicacid-1,4-butanediol-malic acid-citric acid copolyester. A desiredcopolyester can be produced by changing the trifunctional oxycarboxylicacid as needed.

When a bifunctional oxycarboxylic acid is used in combination further,examples of the copolyester thus available include succinicacid-1,4-butanediol-malic acid-lactic acid copolyester, succinicacid-adipic acid-1,4-butanediol-malic acid-lactic acid copolyester,succinic acid-1,4-butanediol-malic acid-tartaric acid-lactic acidcopolyester, succinic acid-adipic acid-1,4-butanediol-malicacid-tartaric acid-lactic acid copolyester, succinicacid-1,4-butanediol-malic acid-citric acid-lactic acid copolyester, andsuccinic acid-adipic acid-1,4-butanediol-malic acid-citric acid-lacticacid copolyester.

The upper limit of the amount of the tri- or higher functional compoundunit is typically 5 mole % or less, preferably 1 mole % or less, stillmore preferably 0.50 mole % or less, especially preferably 0.3 mole % orless based on 100 mole % of all the monomer units constituting thepolyester in order to avoid gelation. When a tri- or higher functionalcompound is used as a copolymerizable component for facilitating theproduction of a polyester having a high degree of polymerization, thelower limit of the using amount at which it exhibits its effect istypically 0.0001 mole % or greater, preferably 0.001 mole % or greater,more preferably 0.005 mole % or greater, especially preferably 0.01 mole% or greater.

For the production of the polyester of the present invention, a chainextender such as carbonate compound or diisocyanate compound can beused. The using amount of it is, in terms of a carbonate bond orurethane bond content, typically 10 mole % or less, preferably 5 mole %or less, more preferably 3 mole % or less based on all the monomer unitsconstituting the polyester. When the polyester of the present inventionis used as a biodegradable resin, a diisocyanate or carbonate bondpresent therein may inhibit the biodegradability so that it is used inthe following amount based on all the monomer units constituting thepolyester. The carbonate bond content is less than 1 mole %, preferably0.5 mole % or less, more preferably 0.1 mole % or less, while theurethane bond content is less than 0.06 mole %, preferably 0.01 mole %or less, more preferably 0.001 mole % or less. The carbonate bond orurethane bond content can be determined by NMR measurement such as ¹³CNMR.

Specific examples of the carbonate compound include diphenyl carbonate,ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate,dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutylcarbonate, ethylene carbonate, diamyl carbonate, and dicyclohexylcarbonate. In addition, carbonate compounds derived from hydroxycompounds, which may be the same or different, such as phenols andalcohols are also usable.

Specific examples of the diisocyanate compound include knowndiisocyanates such as 2,4-tolylene diisocyanate, a mixture of2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate diphenylmethanediisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate,hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, andisophorone diisocyanate.

Production of a high molecular weight polyester using theabove-described chain extender (coupling agent) can be performed in amanner known per se in the art. After completion of thepolycondensation, the chain extender is added under a homogeneous moltenstate to a reaction system in a solventless manner and is reacted with apolyester obtained by the polycondensation.

More specifically, a polyester resin having an increased molecularweight is available by reacting, with the above-described chainextender, a polyester which has been obtained by the catalytic reactionof the diol and the dicarboxylic acid (or anhydride thereof), hassubstantially a hydroxyl group as the terminal group, and has a weightaverage molecular weight (Mw) of 20,000 or greater, preferably 40,000 orgreater. Owing to the use of a small amount of the coupling agent, theprepolymer having a weight-average molecular weight of 20,000 or greateris free from the influence of a remaining catalyst even under severemolten condition. As a result, a high molecular weight polyester can beproduced without generating a gel during the reaction.

Accordingly, when the above-described diisocyanate, for example, is usedas a chain extender for the purpose of increasing the molecular weightfurther, a polyester having a linear structure in which prepolymers eachmade of a diol and a dicarboxylic acid and having a weight averagemolecular weight of 20,000 or greater, preferably 40,000 or greater havebeen chained via a urethane bond derived from the diisocyanate isproduced.

The pressure upon chain extension is typically 0.01 MPa or greater butnot greater than 1 MPa, preferably 0.05 MPa or greater but not greaterthan 0.5 MPa, more preferably 0.07 MPa or greater but not greater than0.3 MPa, with the normal pressure being most preferred.

With respect to the reaction temperature upon chain extension, the lowerlimit is typically 100° C. or greater, preferably 150° C. or greater,more preferably 190° C. or greater, most preferably 200° C. or greater,while the upper limit is typically 250° C. or less, preferably 240° C.or less, more preferably 230° C. or less. Too low reaction temperaturesraise a viscosity and disturb homogeneous reaction. They sometimes tendto need a high stirring power. Too high reaction temperatures tend tocause gelation or decomposition of the polyester simultaneously.

With respect to the chain extension time, the lower limit is typically0.1 minute or greater, preferably 1 minute or greater, more preferably 5minutes or greater, while the upper limit is typically 5 hours or less,preferably 1 hour or less, more preferably 30 minutes or less, mostpreferably 15 minutes or less. Too short extension time tends to disturbthe appearance of addition effect. Too long extension time, on the otherhand, tends to cause gelation or decomposition of the polyestersimultaneously.

As other chain extenders, dioxazoline and silicate esters are usable.Specific examples of the silicate esters include tetramethoxysilane,dimethoxydiphenylsilane, dimethoxydimethylsilane anddiphenyldihydroxysilane.

Although no particular limitation is imposed on the using amount of thesilicate ester from the standpoints of environmental preservation andsafety, a small using amount is sometimes preferred in order to avoidthe possibility of making the operation complicated or adverselyaffecting the polymerization rate. The content of the silicate ester istherefore preferably 0.1 mole % or less, more preferably 10⁻⁵ mole % orless based on all the monomer units constituting the polyester.

Thus, the term “polyester” as used herein is a generic name thatcollectively embraces polyesters, copolyesters, high molecular weightpolyesters having chain-extended (coupled), and modified polyesters.

In the present invention, polyesters substantially free of a chainextender are preferred. A small amount of a peroxide may however beadded in order to heighten the melt tension insofar as a compound havinga low toxicity is added.

In the present invention, a terminal group of the polyester may besealed with a carbodiimide, epoxy compound, a monofunctional alcohol orcarboxylic acid.

As the carbodiimide compound, compounds (including polycarbodiimidecompounds) having, in the molecule thereof, at least one carbodiimidegroup are usable. Specific examples include monocarbodiimide compoundssuch as dicyclohexylcarbodiimide, diisopropylcarbodiimide,dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide,t-butylisopropylcarbodiimide diphenylcarbodiimide,di-t-butylcarbodiimide, di-β-naphthylcarbodiimide andN,N′-di-2,6-diisopropylphenylcarbodiimide. As the polycarbodiimidecompound, those having a degree of polymerization of typically 2 orgreater, preferably 4 or greater, as the lower limit, and typically 40or less, preferably 30 or less as the upper limit are used. Examples ofthem include those prepared by the process as described in U.S. Pat. No.2,941,956; Japanese Patent Publication No. Sho 47-33279; J. Org. Chem.28, 2069-2075 (1963); Chemical Review 1981, Vol. 81 No. 4, pp. 619-621,and the like.

Examples of the organic diisocyanate which is a raw material for theproduction of the polycarbodiimide compound include aromaticdiisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates, andmixtures thereof. Specific examples include 1,5-naphthalenediisocyanate, 4,4′-diphenylmethane diisocyanate,4,4′-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate,1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylenediisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate,xylylene diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethanediisocyanate, methylcyclohexane diisocyanate, tetramethylxylylenediisocyanate, 2,6-diisopropylphenyl isocyanate and1,3,5-triisopropylbenzene-2,4-diisocyanate.

Specific examples of the industrially available polycarbodiimidesinclude “CARBODILITE HMV-8CA” (product of Nisshinbo Industries),“CARBODILITE LA-1” (product of Nisshinbo Industries), “STABAXOL P”(product of Rhine Chemie), and “STABAXOL P100” (product of RhineChemie).

The carbodiimide compounds may be used either singly or as a mixture ofa plurality of them.

<Production of Polyester>

A polyester composed mainly of a diol unit and a dicarboxylic acid unitcan be produced in a manner known per se in the art in the production ofpolyesters. The polymerization reaction for producing polyesters can becarried out under conventionally employed appropriate conditions and noparticular limitation is imposed on them. Described specifically, it canbe produced by the ordinarily employed melt polymerization in which anesterification reaction and/or ester exchange reaction of theabove-described dicarboxylic acid component and diol component, and theoxycarboxylic acid unit or tri- or higher functional component if it isintroduced, is carried out, followed by a polycondensation reactionunder reduced pressure; or by the known thermal dehydration condensationmethod in an organic solvent. From the standpoints of economy andsimplicity of the production steps, melt polymerization in a solventlessmanner is preferred.

In the present invention, when the biomass-resource-derived dicarboxylicacid and/or diol prepared in the above-described manner is used as a rawmaterial for a polyester, the polyester may be produced in a reactiontank whose oxygen concentration is controlled not to exceed a specificvalue during the polyester production reaction. This makes it possibleto suppress coloration of the polyester which will otherwise occur bythe oxidation reaction of a nitrogen compound contained as an impurity,or coloration of the polyester due to a reaction product of dioloxidation, for example, 2-(4-hydroxybutyloxy)tetrahydrofuran produced bythe oxidation reaction of 1,4-butanediol when 1,4-butanediol is used asthe diol. As a result, a polyester having a good hue can be produced.

The term “production reaction” as used herein defines a reaction fromthe starting of temperature elevation after raw materials are charged inan esterification tank to returning of the pressure of the reaction tankfrom reduced pressure to normal pressure or greater after preparation ofa polymer having a desired viscosity under reduced pressure in apolycondensation tank.

No particular limitation is imposed on the lower limit of the oxygenconcentration in the reaction tank during the production reaction, it istypically 1.0×10⁻⁹% or greater, preferably 1.0×10⁻⁷% or greater based onthe total volume of the reaction tank. The upper limit is typically 10%or less, preferably 1% or less, more preferably 0.1% or less, mostpreferably 0.01% or less. Too low oxygen concentrations tend to make thecontrolling step complicated, while too high oxygen concentrations tendto color the polyester markedly because of the above-described reasons.

When the biomass-resource-derived dicarboxylic acid and/or diol obtainedby the above-described process is used as a raw material of a polyester,a stirring rate prior to the termination of the polymerization reactionunder reduced pressure may be controlled. This makes it possible toproduce a biomass-resource-derived polyester which has been inhibitedfrom decomposition and has a high viscosity.

The term “final stirring rate” as used herein means the minimum stirringrotation speed of a stirrer when a polymer having a desired viscosity isprepared by a polycondensation reaction which will be described later.The stopping operation of the stirrer for taking out the polymer thusprepared is not included in the definition of the polycondensationreaction.

With regard to the stirring rate before termination of thepolymerization reaction under reduced pressure, the lower limit istypically 0.1 rpm or greater, preferably 0.5 rpm or greater, morepreferably 1 rpm or greater, while the upper limit is 10 rpm or less,preferably 7 rpm or less, more preferably 5 rpm or less, most preferably3 rpm or less. Too low stirring rates tend to retard the polymerizationrate or cause unevenness in the viscosity of the resulting polymer. Onthe other hand, too high stirring rates tend to decompose the polymer,in the preparation of the biomass-resource-derived polymer having a highimpurity content, due to shear heat. In the invention, it is preferredthat the desired polyester is produced by stirring ordinarily at arotation speed of 10 rpm or less, for 5 minutes or more, preferably 10minutes or more and, more preferably 30 minutes or more.

With regard to the stirring rate at the starting time of thepolymerization under reduced pressure, the lower limit is typically 10rpm or greater, preferably 20 rpm or greater, more preferably 30 rpm orgreater, while the upper limit is typically 200 rpm or less, preferably100 rpm or less, more preferably 50 rpm or less. Too low stirring ratestend to retard the polymerization rate or prepare a polymer having anuneven viscosity. Too high stirring rates, on the other hand, tend tocause, during the preparation of particularly a biomass-resource-derivedpolymer having a high impurity content, decomposition of the resultingpolymer due to shear heat.

The stirring rate during polymerization reaction under reduced pressuremay be decreased continuously or in stages while observing a viscosityincrease of the polyester. More preferably, it is important to set anaverage stirring rate 10 minutes before termination of thepolycondensation reaction under reduced pressure lower than that 30minutes after the initiation of the polycondensation reaction underreduced pressure. By this adjustment, it is possible to suppress thermaldecomposition of a biomass-resource-derived polyester having a highimpurity content and apt to undergo thermal decomposition duringpreparation of it, whereby a polymer can be prepared stably.

By controlling the stirring rate at the time of esterification reactionand/or ester exchange reaction, preparation of a by-product, forexample, tetrahydrofuran when 1,4-butanediol is used as the diol can bereduced and the polymerization rate can be raised.

With regard to the stirring rate at the time of esterification reaction,the lower limit is typically 30 rpm or greater, preferably 50 rpm orgreater, more preferably 80 rpm or greater, while the upper limit is1000 rpm or less, preferably 500 rpm or less. Too low stirring ratestend to deteriorate a distillation efficiency and retard theesterification reaction. They tend to cause, for example, dehydrationreaction or dehydration cyclization of the diol, leading to suchdrawbacks that a imbalance in a diol/dicarboxylic acid ratio occurs,thereby decreasing the polymerization rate and an excessive amount ofthe diol must be charged. Too high stirring rates are, on the otherhand, economically disadvantageous because they consume extra power.

When the biomass-resource-derived dicarboxylic acid is used as a rawmaterial of a polyester, the oxygen concentration and humidity may becontrolled at the time of transfer of the dicarboxylic acid from thestorage tank to the reactor. This makes it possible to prevent corrosioninside a transfer tube which will otherwise occur by a sulfur componentcontained as an impurity. Moreover, coloration due to the oxidationreaction of a nitrogen source can be prevented, making it possible toproduce a polyester with good hue.

As the transfer tube, ordinarily employed tubes such as those made of ametal, those made of a metal having a glass or resin-lined inside, orthose made of glass or resin are usable. From the standpoint ofstrength, tubes made of a metal or those made of a metal having a glassor resin-lined inside are preferred. For the tubes made of a metal,known materials are used. Specific examples include carbon steel,ferrite steel, martensitic stainless steels such as SUS410, austeniticstainless steels such as SUS310, SUS304 and SUS316, clad steel, castiron, copper, copper alloy, aluminum, inconel, hastelloy and titanium.

Although no particular limitation is imposed on the lower limit of theoxygen concentration in the transfer tube based on the total volume ofthe transfer tube, it is typically 0.00001% or greater, preferably 0.01%or greater. The upper limit is, on the other hand, typically 16% orless, preferably 14% or less, more preferably 12% or less. Too lowoxygen concentrations are economically disadvantageous because they maymake the equipment investment or control step complicated. Too highoxygen concentrations, on the other hand, tend to enhance the colorationof a polymer thus prepared.

Although no particular limitation is imposed on the lower limit of thehumidity in the transfer tube, it is typically 0.0001% or greater,preferably 0.001% or greater, more preferably 0.01% or greater, mostpreferably 0.1% or greater. The upper limit is 80% or less, preferably60% or less, more preferably 40% or less. Too low humidities tend to beeconomically disadvantageous because the step for humidity controlbecomes too complicated. Too high humidities tend to cause problems suchas corrosion of the storage tank or pipes. When the humidity is toohigh, problems such as attachment of the dicarboxylic acid to thestorage tank or pipes and blocking of the dicarboxylic acid occur andsuch attachment phenomena tend to accelerate the corrosion of the pipes.

The lower limit of the temperature in the transfer tube is typically−50° C. or greater, preferably 0° C. or greater. The upper limit is, onthe other hand, typically 200° C. or less, preferably 100° C. or less,more preferably 50° C. or less. Too low temperatures tend to increasethe storage cost, while too high temperatures tend to cause dehydrationreaction of the dicarboxylic acid simultaneously.

The pressure in the transfer tube is typically from 0.1 kPa to 1 MPa,but the transfer tube is used under the pressure of about 0.05 MPa orgreater but not greater than 0.3 MPa from the viewpoint of operability.

When a polyester is produced, the diol is used in a substantiallyequimolar amount to 100 moles of the dicarboxylic acid or derivativethereof, however, it is usually employed in 0.1 to 20 moles % excess inconsideration of the distillation during the esterification reactionand/or ester exchange reaction and/or polycondensation reaction. When anaromatic polyester is produced, on the other hand, the number ofterminal carboxyl groups tend to increase so that the diol is used in 10to 60 mole % excess based on 100 moles of the dicarboxylic acid orderivative thereof.

The polycondensation reaction is preferably performed in the presence ofa polymerization catalyst. The polymerization catalyst may be added inany stage without particular limitation insofar as it is prior to thepolycondensation reaction. It may be added at the time of charging rawmaterials or at the time of starting pressure reduction.

As the polymerization catalyst, compounds containing a metal element inGroup I to Group XIV of the periodic table except hydrogen and carbonare usable. Specific examples include organic-group-containing compoundssuch as carboxylates, alkoxy salts, organic sulfonates and β-diketonatesalts each containing at least one metal selected from the groupconsisting of titanium, zirconium, tin, antimony, cerium, germanium,zinc, cobalt, manganese, iron, aluminum, magnesium, calcium, strontium,sodium and potassium, and inorganic compounds such as oxides or halidesof the above-described metals, and mixtures thereof. These catalystcomponents may be contained in the raw materials of a polyester derivedfrom biomass resources because of the above-described reason. In thiscase, the raw materials may be used as are as metal-containing rawmaterials without purifying them particularly. Polyesters having ahigher degree of polymerization are sometimes prepared easily by usingraw materials having a lower content of metal elements in Group I suchas sodium or potassium. In such a case, raw materials purified untilthey become substantially free from metal elements in Group I arepreferred.

Of these, metal compounds containing titanium, zirconium, germanium,zinc, aluminum, magnesium, or calcium, or a mixture thereof arepreferred, of which titanium compounds, zirconium compounds andgermanium compounds are especially preferred.

The catalyst is preferably a compound in the liquid form or compoundsoluble in an ester oligomer or polyester, because the catalyst in themolten or dissolved form at the time of polymerization increases thepolymerization rate.

As the titanium compounds, tetraalkyl titanates are preferred. Specificexamples include tetra-n-propyl titanate, tetraisopropyl titanate,tetra-n-butyl titanate, tetra-t-butyl titanate, tetraphenyl titanate,tetracyclohexyl titanate, and tetrabenzyl titanate, and mixturesthereof. In addition, titanium (oxy)acetylacetonate, titaniumtetraacetylacetonate, titanium (diisoproxide) acetylacetonate, titaniumbis(ammonium lactate)dihydroxide, titanium bis(ethylacetoacetate)diisopropoxide, titanium (triethanolaminate) isopropoxide,polyhydroxytitanium stearate, titanium lactate, titaniumtriethanolaminate and butyl titanate dimer are also preferred. Moreover,titanium oxide and composite oxide containing titanium and silicon (forexample, titania/silica composite oxide (product name: C-94), product ofAcordis Industrial Fibers) are also preferred. Of these, tetra-n-propyltitanate, tetraisopropyl titanate, tetra-n-butyl titanate, titanium(oxy)acetylacetonate, titanium tetraacetylacetonate, titaniumbis(ammonium lactate)dihydroxide, polyhydroxytitanium stearate, titaniumlactate, butyl titanate dimer, titanium oxide, and titania/silicacomposite oxide (for example, product name: C-94, product of AcordisIndustrial Fibers) are more preferred, with tetra-n-butyl titanate,titanium (oxy)acetylacetonate, titanium tetraacetylacetonate,polyhydroxytitanium stearate, titanium lactate, butyl titanate dimer,and titania/silica composite oxide (product name: C-94; product ofAcordis Industrial Fibers) being still more preferred. In particular,tetra-n-butyl titanate, polyhydroxytitanium stearate,titanium(oxy)acetylacetonate, titanium tetraacetylacetonate, andtitania/silica composite oxide (product name: C-94; product of AcordisIndustrial Fibers) are preferred.

Specific examples of the zirconium compound include zirconiumtetraacetate, zirconium acetate hydroxide, zirconiumtris(butoxy)stearate, zirconyl diacetate, zirconium oxalate, zirconyloxalate, potassium zirconium oxalate, polyhydroxyzirconium stearate,zirconium ethoxide, zirconium tetra-n-propoxide, zirconiumtetraisopropoxide, zirconium tetra-n-butoxide, zirconiumtetra-t-butoxide, and zirconium tributoxyacetylacetonate, and mixturesthereof. In addition, zirconium oxide and composite oxides containingzirconium and silicon are preferred. Of these, zirconyl diacetate,zirconium tris(butoxy)stearate, zirconium tetraacetate, zirconiumacetate hydroxide, zirconium ammonium oxalate, potassium zirconiumoxalate, polyhydroxyzirconium stearate, zirconium tetra-n-propoxide,zirconium tetraisopropoxide, zirconium tetra-n-butoxide, and zirconiumtetra-t-butoxide are preferred, of which zirconyl diacetate, zirconiumtetraacetate, zirconium acetate hydroxide, zirconiumtris(butoxy)stearate, ammonium zirconium oxalate, zirconiumtetra-n-propoxide, and zirconium tetra-n-butoxide are more preferred.Particularly, zirconium tris(butoxy)stearate is preferred because apolyester having a high degree of polymerization and free of colorationis easily available.

Specific examples of the germanium compound include inorganic germaniumcompounds such as germanium oxide and germanium chloride and organicgermanium compounds such as tetraalkoxygermanium. In view of price andavailability, germanium oxide, tetraethoxygermanium,tetrabutoxygermanium, and the like are preferred, with germanium oxidebeing especially preferred.

When the above-described metal compound is used as the polymerizationcatalyst, the lower limit of the using amount of it is, in terms of ametal amount based on the resulting polyester, typically 5 ppm orgreater, preferably 10 ppm or greater and the upper limit is typically30000 ppm or less, preferably 1000 ppm or less, more preferably 250 ppmor less, especially preferably 130 ppm or less. Too large amounts of thecatalyst are not only economically disadvantageous but also deterioratethe thermal stability of the polymer. Too small amounts, on the otherhand, lower the polymerization activity and tend to induce decompositionof the polymer during the preparation thereof. The concentration of theterminal carboxyl group of the resulting polyester decreases with areduction in the using amount of the catalyst so that a method ofreducing the using amount of the catalyst is preferred.

With regard to the temperature of the esterification reaction/or esterexchange reaction of the dicarboxylic acid component and diol component,the lower limit is typically 150° C. or greater, preferably 180° C. orgreater and the upper limit is typically 260° C. or less, preferably250° C. or less. The reaction atmosphere is typically an inert gasatmosphere such as nitrogen or argon. The reaction pressure is typicallyfrom normal pressure to 10 kPa, with normal pressure being preferred.

With regard to the reaction time, the lower limit is typically 1 hour orgreater, while the upper limit is typically 10 hours or less, preferably4 hours or less.

The polycondensation reaction after the esterification reaction and/orester exchange reaction of the dicarboxylic acid component and the diolcomponent is performed under vacuum while controlling the lower limit ofthe pressure to typically 0.01×10³ Pa or greater, preferably 0.05×10³ Paor greater and the upper limit to typically 1.4×10³ Pa or less,preferably 0.4×10³ Pa or less. With regard to the reaction temperatureduring the polycondensation reaction, the lower limit is typically 150°C. or greater, preferably 180° C. or greater and the upper limit istypically 260° C. or less, preferably 250° C. or less. The lower limitof the reaction time is typically 2 hours or greater, while the upperlimit is typically 15 hours or less, preferably 10 hours or less.

In the invention, as a reactor for producing the polyester, knownvertical or horizontal stirred tank reactors can be used. For example, amethod of carrying out melt polymerization, which has a step of anesterification reaction and/or ester exchange reaction and a step ofpolycondensation under reduced pressure, in two stages in reactors whichare the same or different and using, as a reactor for polycondensationunder reduced pressure, a stirred tank reactor fitted with adecompression exhaust tube connecting a vacuum pump and the reactor canbe employed. And, a method of recovering volatile components generatedduring the polycondensation reaction and unreacted monomers in acondenser in the middle of the decompression exhaust tube connecting thevacuum pump and the reactor can be employed preferably.

In the invention, processes used for producing an aliphatic esterinclude a process of carrying out an esterification reaction and/orester exchange reaction between a dicarboxylic acid component containingthe above-described aliphatic dicarboxylic acid and an aliphatic diolcomponent and then increasing the degree of polymerization of thepolyester while distilling off the diol formed by the ester exchangereaction of the terminal alcohol group of the polyester; and a processof increasing the degree of polymerization of the polyester whiledistilling off the aliphatic dicarboxylic acid and/or cyclic acidanhydride thereof from the terminal aliphatic carboxyl group of thepolyester. In the latter process, the aliphatic carboxylic acid and/orcyclic acid anhydride thereof is removed typically by distilling off thealiphatic dicarboxylic acid and/or cyclic acid anhydride thereof byheating during the polycondensation reaction under reduced pressure,that is, a latter-stage reaction of the melt polymerization. Under thepolycondensation reaction conditions, the aliphatic dicarboxylic acid iseasily converted into the cyclic acid anhydride thereof so that it isusually distilled off by heating in the form of a cyclic acid anhydride.During this distillation, linear or cyclic ether and/or diol derivedfrom the diol may be removed together with the aliphatic dicarboxylicacid and/or cyclic acid anhydride thereof. It is preferred to employ amethod of distilling off the cyclic monomers of the dicarboxylic acidcomponent and diol component together, because it improves apolymerization rate.

On the other hand, in producing an aromatic polyester, the formerprocess of heightening the degree of polymerization of the polyesterwhile using excess diol and distilling off the added portion of the diolas described above is preferred.

During the production process of the polyester or after production ofthe polyester, various additives, for example, a plasticizer,ultraviolet stabilizer, coloration preventive, matting agent, deodorant,flame retardant, weathering stabilizer, antistatic, yarn frictionreducing agent, release agent, antioxidant, ion exchange agent, andinorganic fine particles and organic compounds as coloring pigments maybe added as needed within a range not impairing the properties of thepolyester. Examples of the coloring pigment include inorganic pigmentssuch as carbon black, titanium oxide, zinc oxide and iron oxide andorganic pigments such as cyanine, styrene, phthalocyanine,anthraquinone, perynone, isoindolinone, quinophthalone, quinocridone andthioindigo. A quality modifier such as calcium carbonate or silica canalso be added.

In the present invention, the temperature of the polyester when it istaken out from a polymerization reactor after completion of thepolymerization reaction may be controlled. This makes it possible totake out a high viscosity polyester while suppressing thermaldecomposition of it.

With regard to the temperature of the polyester when it is taken outfrom the polymerization reactor, assuming that the resin temperature atthe time when the pressure of the polymerization reactor is returnedfrom the reduced pressure to the normal pressure or greater aftercompletion of the polymerization is Te, the lower limit is (Te−50)° C.or greater, preferably (Te−30)° C. or greater, more preferably (Te−20)°C. or greater, most preferably (Te−10)° C. or greater, while the upperlimit is (Te+20)° C. or less, preferably (Te+10)° C. or less, morepreferably Te° C. or less. Too low temperatures tend to cause a problemin productivity because an increase in the viscosity of the polyester atthe time of discharging it from the reactor disturbs smooth discharge ofit. At too high temperatures, on the other hand, the thermaldecomposition of the polyester occurs considerably.

The temperature of the polyester at the time of discharging it from thetank can be measured by a thermocouple attached inside thepolymerization reactor to measure the temperature thereof.

In the present invention, the polyester in the form of strands taken outfrom the polymerization reactor may be brought into contact with anaqueous medium of a specific temperature or less after completion of thepolymerization reaction. This enables to obtain a high viscositypolyester while suppressing the decomposition of it.

Although no particular limitation is imposed on the medium for coolingthe polyester, examples include diols such as ethylene glycol, alcoholssuch as methanol and ethanol, acetone and water. Of these, water is mostpreferred. These aqeuous solvents may be used in combination of two ormore thereof.

With regard to the temperature of the solvent, the lower limit istypically −20° C. or greater, preferably −10° C. or greater, morepreferably 0° C. or greater, most preferably 4° C. or greater, while theupper limit is typically 20° C. or less, preferably 15° C. or less, morepreferably 10° C. or less. Too low temperatures tend to be economicallydisadvantageous because they increase the operation cost of coolingequipment of the medium. Too high temperatures tend to cause markedthermal decomposition of the polyester when it is taken out in the formof strands.

With regard to the cooling time of the polyester, the lower limit istypically 0.1 second or greater, preferably 1 second or greater, morepreferably 5 seconds or greater, most preferably 10 seconds or greater,while the upper limit is typically 5 minutes or less, preferably 2minutes or less, more preferably 1 minute or less, most preferably 30seconds or less. Too short cooling time tends to cause marked fusion ofstrands and disturbs pelletization. Too long cooling time tends to acton productivity adversely.

Although no particular limitation is imposed on the cooling method,examples include a method of taking out the polyester from thepolymerization reactor in the form of strands and causing it to go intothe cooling medium or a method of showering the strands with the coolingmedium.

<Pellets of Polyester>

After completion of the polymerization reaction, the polyester taken outfrom the polymerization reactor in the form of strands is cooled withwater, air or the like. Then, it is pelletized by a known fixed orrotary cutter or pelletizer. The pellets thus obtained may be stored.

The shape of the pellets is typically spherical or cylindrical with acircular or elliptical cross-section.

The diameter of the polyester pellets is adjusted by controlling thediameter of a discharging outlet of the polymerization reactor,discharging rate of strands, taking-up rate, cutting speed or the like.Described specifically, it is adjusted, for example, by controlling thepressure in the reactor at the time of discharging the polymer therefromor a cutting speed of a rotary strand cutter.

With respect to the diameter of the polyester pellets thus obtained, thelower limit (minimum diameter) is typically 0.1 mm or greater,preferably 0.2 mm or greater, more preferably 0.5 mm or greater, mostpreferably 1 mm or greater, while the upper limit (maximum diameter) is20 mm or less, preferably 10 mm or less, more preferably 7 mm or less,most preferably 4 mm or less. Too small diameters tend to cause markeddeterioration of the pellets due to hydrolysis during the storage of thepellets. Too large diameters, on the other hand, tend to causeunevenness in the product because of inferiority in the feed stabilityof the pellets at the time of molding.

In the polyester pellets of the present invention, the proportion ofpowders having the maximum diameter less than 1 mm is preferably 2.0 wt.% or less, more preferably 1.0 wt. % or less. When the proportion of thepowder having the maximum diameter less than 1 mm is too large, presenceof the powder increases the residence time of the pellets in the moldingmachine owing to inferior feed stability of the pellets in the screw ofthe machine at the time of melt molding, and thermal deterioration whichmay occur owing to an increase in their surface area causes mixing offoreign matters such as scorch or hard spots in the molded product,resulting in the problems such as deterioration in mechanical strengthor appearance of the molded product.

The term “diameter of the polyester pellets” as used herein means thediameter or length of the cross-section of the polyester pellets. Theterm “the cross-section of the polyester pellets” means thecross-section of the polyester pellets having the maximumcross-sectional area.

In the present invention, a water content in the polyester pelletsduring storage may be controlled. Although no particular limitation isimposed on the lower limit of the water content, as a mass ratio, basedon the polyester, it is typically 0.1 ppm or greater, preferably 0.5 ppmor greater, more preferably 1 ppm or greater, most preferably 10 ppm orgreater. The upper limit is typically 3000 ppm or less, preferably 2000ppm or less, more preferably 1000 ppm or less, especially preferably 800ppm or less, most preferably 500 ppm or less. Too low water contentstend to be economically disadvantageous because they make the equipmentor controlling step complicated. In addition, it takes much time fordrying so that they tend to cause coloration of the polyester ordeterioration thereof such as generation of hard spots. Too high watercontents, on the other hand, tend to cause marked deterioration of thepolyester due to hydrolysis during storage of pellets.

The water containing amount (water content) in the polyester pellets maybe measured by heating and melting 0.5 g of a pellet sample at 200° C.by using a moisture vaporizer (“VA-100”, product of Mitsubishi Chemical)to evaporate water from the sample and then determining the total watercontent thus evaporated by coulometric titration based on the principleof the Karl Fischer reaction by using a trace moisture meter (“CA-100”,product of Mitsubishi Chemical).

In the polyester pellets of the present invention, the polyesterundergoes hydrolysis by moisture and has deteriorated properties so thatthe pellets may be stored in a hermetically sealed condition. The term“hermetically sealed condition” as used herein means a condition underwhich the dry state of the polyester can be maintained.

Examples of the hermetically sealing method include storage in a spaceequipped with a hermetically sealing function; storage in a bag equippedwith a hermetically sealing function; covering the polyester pelletswith a sheet equipped with a hermetically sealing function; and storagein a silo under a dry atmosphere (including dry air or circulation ofnitrogen). Of these, storage in a bag equipped with a hermeticallysealing function is preferred.

The bag is preferably made of a highly airtight material. Films orsheets made of a synthetic resin are preferred. Specific examplesinclude sheets made of a polyolefin resin such as polyethylene orpolypropylene or polyvinyl chloride resin and these sheets reinforcedwith a polyester or polyamide film or various fiber base materials.These sheets may have a barrier layer stacked thereover as needed forblocking water vapor or oxygen. A composite film such aspolyester/aluminum/polyethylene film is one example of such a filmstack.

Various packaging materials having such properties are commerciallyavailable. Of these, those easily sealed by heating are preferred. Thematerials are formed into packaging bags by heat fusion and/or sewing.

No particular limitation is imposed on the shape of the packaging bagand known bag shapes such as flat bag, gadget bag, square-bottom bag andflexible containers can be employed. These bags preferably have a bottomsurface in consideration that the cross-sectional shape of the base ofthe package when the pellets are actually packaged therein is madesubstantially rectangular. Of these, gadget bags, square-bottom bags andflexible containers are preferred. Bags having a substantiallyrectangular bottom shape are more preferred because the packages caneasily have a base with a substantially rectangular cross-section whilehaving the pellets therein.

The polyester pellets derived from biomass sources contain impurities sothat they are susceptible to coloration or deterioration. They maytherefore be stored with light shielding.

Although no particular limitation is imposed on the light shieldingmethod insofar as it can shield the polyester from the light, specificexamples include storage in a space equiped with a light shieldingfunction, storage in a bag equipped with a light shielding function, andcovering the polyester pellets with a sheet equipped with a lightshielding function. Of these, storage in a bag equipped with a lightshielding function is preferred.

With respect to the light shielding degree, the upper limit of theilluminance of the space is typically 300 lux or less, preferably 70 luxor less, more preferably 1 lux or less, most preferably 0.001 lux orless, while the lower limit is not particularly limited. Too highilluminance tends to cause marked coloration of the polyester, while toolow illuminance is economically disadvantageous because control of it isdifficult.

With respect to the temperature during the storage of the polyesterpellets, the lower limit is −50° C. or higher, preferably −0.30° C. orhigher, more preferably 0° C. or higher, while the upper limit is 80° C.or less, preferably 50° C. or less, more preferably 30° C. or less.Storage at room temperature is most preferred because it does not needtemperature control step. Too low temperatures are economicallydisadvantageous because they make the control step complicated. Too hightemperatures, on the other hand, tend to cause marked deterioration ofthe polyester.

Although no particular limitation is imposed on the external pressureduring the storage of the polyester pellets, it is typically atmosphericpressure (normal pressure).

A polyester composition which will be described later may be storedunder the above-described conditions after pelletization.

<Physical Properties of Polyester>

The polyester pellets of the present invention are available from thepolyester having the following physical properties. Their physicalproperties do not deteriorate even after storage.

The physical properties of the polyester of the present invention willbe explained using a polyester composed of an aliphatic diol and analiphatic dicarboxylic acid such as polybutylene succinate andpolybutylene succinate adipate, as an example. It has similar propertiesto those of the general-purpose polymers, more specifically, it has adensity from 1.2 to 1.3 g/cm³, melting point from 80 to 120° C., tensilestrength from 30 to 80 Mpa, tensile elongation at break from 300 to600%, Young modulus from 400 to 700 MPa, Izod impact strength from about5 to 20 kJ/m², and glass transition point from −45 to −25° C. If thepolyester is used for a special purpose, it can have properties fallingwithin more-wide desired ranges without limitation to theabove-described ranges. Moreover, it can have melting point, melt indexand melt viscoelasticity sufficient to permit preparation of a moldedproduct by various molding means. These properties can be controlledfreely by changing the kind of polyester raw materials or additivesthereto, polymerization conditions, or molding conditions in accordancewith the intended use.

Detailed ranges of the typical physical properties of the polyester ofthe present invention will hereinafter be disclosed.

Although no particular limitation is imposed on the melting point of thepolyester of the present invention, it is typically from 40 to 270° C.,preferably from 50 to 230° C., more preferably from 60 to 130° C. Themelting point is determined by the above-described components so that itis possible to produce a polyester having a melting point within theabove-described range by selecting proper components.

With respect to the number-average molecular weight, in terms ofpolystyrene, of the polyester of the present invention, the lower limitis typically 5000 or greater, preferably 10000 or greater, morepreferably 15000 or greater, while the upper limit is typically 500000or less, preferably 300000 or less.

With respect to the composition ratio of the copolyester, a molar ratioof the diol unit to the dicarboxylic acid unit must be substantially 1.

The content of nitrogen atoms contained in the polyester of the presentinvention other than those contained in the covalently bonded functionalgroups is 1000 ppm or less based on the mass of the polyester. Thecontent of nitrogen atoms in the polyester other than those contained inthe covalently bonded functional groups is preferably 500 ppm or less,more preferably 100 ppm or less, still more preferably 50 ppm or less,of which 40 ppm or less is preferred, 30 ppm or less is more preferredand 20 ppm or less is most preferred. The content of nitrogen atoms inthe polyester other than those contained in the covalently bondedfunctional groups is mainly derived from nitrogen atoms in the rawmaterials. The content of nitrogen atoms in the polyester other thanthose contained in the covalently bonded functional groups is preferably1000 ppm or less because if so, coloration or generation of foreignmatters at the time of molding is suppressed and heat- or light-induceddeterioration or hydrolysis of the molded product does not occur easily.

In addition, for some using purpose, the content of nitrogen atoms inthe polyester other than those contained in the covalently bondedfunctional groups not greater than 100 ppm or less is preferred, becausecoloration or generation of foreign matters of the polyester issuppressed at such a content. The lower the nitrogen atom content, themore eminent its effect becomes.

On the other hand, the content of nitrogen atoms in the polyester otherthan those contained in the covalently bonded functional groups ispreferably 0.01 ppm or greater, more preferably 0.05 ppm or greater,still more preferably 0.1 ppm or greater, especially preferably 1 ppm orgreater. Nitrogen atom contents less than 0.01 ppm are disadvantageousfrom the standpoint of energy because a certain load is applied duringthe purification of the raw materials. In addition, an adverse effect onthe environment cannot be neglected.

Nitrogen atom contents of 1 ppm or greater are preferred because theyaccelerate a biodegration rate in a soil when the polyester is analiphatic polyester. Use of the raw materials having a nitrogen atomcontent falling within the above-described range is effective foraccelerating biodegradability of the polyester thus obtained withoutdecreasing the polymerization rate of the polyester in thepolymerization reaction. The nitrogen atom content can be measured bychemiluminescence, a conventionally known method which will be describedlater. The term “ppm” as used herein means mass ppm.

The term “covalently bonded functional groups in the polyester” as usedherein means urethane functional groups derived from the above-describeddiisocyanate compounds or carbodiimide compounds, unreacted isocyanatefunctional groups, urea functional groups and isourea functional groups,and unreacted carbodiimide functional groups. Accordingly, in theinvention, the “content of nitrogen atom in the polyester other thanthose contained in the covalently bonded functional groups” is a valueobtained by subtracting, from the total nitrogen atom content in thepolyester, the nitrogen atom contents belonging to the urethanefunctional groups, unreacted isocyanate functional groups, ureafunctional groups, and isourea functional groups, and unreactedcarbodiimide functional groups. The content of the urethane functionalgroups, unreacted isocyanate functional groups, urea functional groups,and isourea functional groups, and unreacted carbodiimide functionalgroups can be determined from the above-described ¹³C-NMR,spectrophotometry such as IR, or a feeding amount at the time ofproducing the polyester.

With regard to a ratio of the nitrogen content in the polyester of thepresent invention to an ammonia content in the raw materials ispreferably 0 or greater but not greater than 0.9, more preferably 0 orgreater but not greater than 0.6, especially preferably 0.3 or less.

With regard to the sulfur atom content in the polyester of the presentinvention, the upper limit is 50 ppm or less, preferably 5 ppm or less,more preferably 3 ppm or less, most preferably 0.3 ppm or less in termsof atoms based on the mass of the polyester. Although no particularlimitation is imposed on the lower limit, it is 0.0001 ppm or greater,preferably 0.001 ppm or greater, more preferably 0.01 ppm or greater,especially preferably 0.05 ppm or greater, most preferably 0.1 ppm orgreater. Too high sulfur contents tend to deteriorate thermal stabilityor hydrolysis resistance of the polyester. The system with a too lowsulfur atom content tends to be economically disadvantageous in theproduction of the polyester because of a marked increase in thepurification cost.

In the polymer of the present invention, the polyester obtained usingraw materials derived from biomass resources tends to contain thereinvolatile organic components, for example, tetrahydrofuran andacetaldehyde. The upper limit of their content in the polyester istypically 10000 ppm or less, preferably 3000 ppm or less, morepreferably 1000 ppm or less, most preferably 500 ppm or less. Althoughno particular limitation is imposed on the lower limit, it is typically1 ppb or greater, preferably 10 ppb or greater, more preferably 100 ppbor greater. Too high volatile contents may become responsible for anodor and in addition, may cause foaming during melt molding or worseningof storage stability. The system with a too low volatile content ispreferred, but is economically disadvantageous because it needs aremarkably large amount of equipment investment and also tremendousproduction time.

The reduced viscosity (ηsp/c) of the polyester produced in the presentinvention is 0.5 or greater because the resulting polyester can haveenough mechanical properties for its practical use. In particular, 1.0or greater is preferred, with 1.8 or greater being more preferred andwith 2.0 or greater being especially preferred. The upper limit of thereduced viscosity (ηsp/c) is typically 6.0 or less, preferably 5.0 orless, more preferably 4.0 or less in view of operability such as easydischarge and moldability or formability, each of the polyester afterpolymerization reaction.

The reduced viscosity in the present invention is measured under thefollowing conditions:

[Measurement Conditions of Reduced Viscosity (ηsp/c)]

Viscosity tube: Ubbelohde's viscosity tube

Measurement temperature: 30° C.

Solvent: phenol/tetrachloroethane (1:1 weight ratio) solution

Polyester concentration: 0.5 g/dl

The polyester of the present invention is preferably soluble uniformlywhen 0.5 g of it is dissolved in a phenol/tetrachloroethane (1:1 weightratio) solution (volume: 1 dl) at room temperature. If an insolublecomponent of the polyester appears, the amount of an insoluble componentis typically 1 wt. % or less, more preferably 0.1 wt. % or less,especially preferably 0.01 wt. % or less in the total amount of thepolyester.

The concentration of the terminal carboxyl group in the polyester of thepresent invention is typically 100 equivalents/metric ton or less, morepreferably 50 equivalents/metric ton or less, especially preferably 35equivalents/metric ton or less, more preferably 25 equivalents/metricton or less, while it is 0.1 equivalent/metric ton or greater,preferably 0.5 equivalent/metric ton or greater, especially 1equivalent/metric ton or greater. Too high concentrations tend todeteriorate thermal stability of the polymer at the time of its moldingor hydrolysis resistance during a relatively long period of use orstorage. The polymer having a too low concentration of carboxyl groupsis preferred, but is economically disadvantageous because it requires asubstantial equipment investment and also much time for its production.

Presence of a large amount of nitrogen-containing compounds orsulfur-containing compounds in the dicarboxylic acid and/or diol tendsto cause an increase in the concentration of terminal carboxyl groups inthe polymer, because such impurities become crosslinking points of thepolymer or accelerate thermal decomposition reaction of the polymer. Inorder to control the concentration of terminal carboxyl groups withinthe above-described range, a method of controlling the amount of thenitrogen-containing compounds or sulfur-containing compounds within theabove-described range, a method of reducing the using amount of thecatalyst, or a method of producing the polymer at lower polymerizationtemperature is preferably employed.

The amount of terminal carboxyl groups is typically calculated by aknown titration method. In the present invention, it is a value obtainedby dissolving the polyester thus obtained in benzyl alcohol andconducting titration with 0.1N NaOH and is a carboxyl equivalent per1×10⁶ g.

The polyester produced by the present invention is preferably a lesscolored polyester. With respect to the yellowness (YI) of the polyesterof the present invention, the upper limit is typically 50 or less,preferably 30 or less, more preferably 20 or less, still more preferably15 or less, especially preferably 10 or less. Although no particularlimitation is imposed on the lower limit, it is typically −20 orgreater, preferably −10 or greater, more preferably −5 or greater,especially preferably −3 or greater, most preferably −1 or greater. Thepolyester having a high YI has the drawback that its use for, forexample, film or sheet is limited. The polyester having a low YI, on theother hand, is preferred, but may be economically disadvantageousbecause production of such a polymer requires a complicated productionprocess and substantial equipment investment. In the present invention,the YI is a value as measured by the method based on JIS K7105.

<Polyester Composition>

A polyester composition is available by blending (kneading) thealiphatic polyester obtained in the above-described process with aconventionally known resin. As such a resin, variousconventionally-known general-purpose resins such as thermoplasticresins, biodegradable resins and natural resins are usable.Biodegradable polymers and general-purpose thermoplastic resins arepreferred. They may be used either singly or as a mixture of two or morethereof. These various resins may be derived from biomass resources.

The aliphatic polyester of the present invention is blended (kneaded)with a known resin to yield a polyester composition having desired andwide range of properties. For example, a blending ratio is notparticularly limited because physical properties of the composition varygreatly with a blending ratio. A composition obtained by blendingpolybutylene succinate and polylactic acid, which will be describedlater, can have properties similar to those of the general-purposepolymers, more specifically, it has a tensile strength from 30 to 60Mpa, tensile elongation at break from 3 to 400%, Young modulus intension from 500 to 3000 Mpa, tensile yield strength from 30 to 50 Mpa,flexural strength from 30 to 100 Mpa, flexural modulus from 600 to 4000Mpa, and Izod impact test strength from 5 to 20 kJ/m². A polyestercomposition obtained by blending with a flexible aromatic polyester alsocan have physical properties similar to those of the general-purposepolymers, more specifically, it has a tensile strength from 30 to 70Mpa, tensile elongation at break from 400 to 800% and tensile yieldstrength from 10 to 30 Mpa. A polyester composition obtained by blendingwith a general-purpose resin such as nylon, polycarbonate, polyacetal,ABS, PET or polystyrene can have physical properties similar to those ofgeneral-purpose polymers, more specifically, it has a density from 1 to1.4 g/cm³, melting point from 150 to 270° C., tensile strength from 30to 80 Mpa, tensile elongation at break from 100 to 600%, and glasstransition point from −85 to 150° C. These properties can be adjustedfreely by changing the kind of the raw materials of polyester or variousresins, a ratio of blended amount or molding conditions depending on theusing purpose.

The general-purpose thermoplastic resin to be blended with thebiomass-resource-derived polyester of the present invention can beselected desirably from general-purpose thermoplastic resins such aspolyesters derived from petroleum which will be described later,polyvinyl acetate, polyvinyl alcohol, polyester, polycarbonate andpolyamide. In this case, compatibility with the biomass-resource-derivedpolyester must be considered. A blending amount is also an importantfactor for appropriately retaining the properties of thebiomass-resource-derived polyester of the present invention. Theblending amount of the biomass-resource-derived polyester is typicallyfrom 99.9 to 20 wt. % and it can be blended with from about 0.1 to 80wt. % of the general-purpose plastic resin. In order to retain theproperties of the biomass-resource-derived polyester such asbiodegradability, however, the blending amount of the general-purposethermoplastic resin is reduced to from 50 to 1 wt. %, preferably fromabout 30 to 3 wt. %, though depending on the purpose. Then, it ispossible to impart predetermined physical properties to the polyesterwhile retaining the biodegradability.

Examples of the biodegradable polymer include aliphatic polyesterresins, polycaprolactone, polylactic acid, polyvinyl alcohol,polyethylene succinate, polybutylene succinate, polysaccharides andother biodegradable resins.

With respect to the blending amount of the biodegradable polymers, whenbiodegradable resins are employed as both resins for imparting onlybiodegradability to the resulting composition, appropriatebiodegradability appears even by blending from about 0.1 to 99.9 wt. %of the biodegradable polymer with from 99.9 to 0.1 wt. % of thebiomass-resource-derived polyester of the present invention. From theviewpoint of the biomass-resource-derived polyester of the presentinvention, however, it is preferred to blend from 99.9 to 40 wt. % ofthe biomass-resource-derived polyester with from about 0.1 to 60 wt. %of the biodegradable polymer, with the blending of the biodegradablepolymer in an amount of from about 5 to 50 wt. % being more preferred.

Examples of the natural resin or polysaccharide to be incorporated inthe biomass-resource-derived polyester of the present invention includecellulose acetate, chitosan, cellulose, chroman indene, rosin, ligninand casein. These natural resins and polysaccharides have a property ofdecaying, in their essential natural state, in the presence of water andair and returning to the soil or becoming a fertilizer. It is possibleto mix from 99.9 to 0.1 wt. % of the biomass-resource-derived polyesterof the present invention with from about 0.1 to 99.9 wt. % of thenatural resin or polysaccharide. It is more preferred to mix from about5 to 50 wt. % of the natural resin or polysaccharide in order to retainnot only biodegradability necessary for the biomass-resource-derivedpolyester but also various properties such as mechanical properties,water resistance and weather resistance which the plastic are requiredto have essentially.

Compatibility between the biomass-resource-derived polyester of thepresent invention and the natural resin or polysaccharide is also aproblem. If this problem is overcome, when a material made of acomposition composed of the biomass-resource-derived polyester of thepresent invention and the natural resin is discarded after use, thedecomposition of the natural resin or polysaccharide occurs and thematerial may be effective as a soil improver or fertilizer, though earlybiodegradation and disappearance cannot be expected. Such a polyesterresin is sometimes recommended to be discarded positively to nature,particularly to soil so that the material which has overcome the problemof compatibility has increased significance as a green plastic product.Specific compositions of each resin will next be disclosed, but notparticularly limited thereto.

Examples of the aliphatic polyester resins include aliphatic polyesterresins having, as essential components, aliphatic and/or alicyclic diolunits and aliphatic and/or alicyclic dicarboxylic acid unit andaliphatic oxycarboxylic acid resins.

Specific examples of the aliphatic and/or alicyclic diol unitconstituting the aliphatic polyester resin include ethylene glycol unit,diethylene glycol unit, triethylene glycol unit, polyethylene glycolunit, propylene glycol unit, dipropylene glycol unit, 1,3-butanediolunit, 1,4-butanediol unit, 3-methyl-1,5-pentanediol unit, 1,6-hexanediolunit, 1,9-nonanediol unit, neopentyl glycol unit, polytetramethyleneglycol unit and 1,4-cyclohexanedimethanol unit. These units may be usedas a mixture of two or more of them.

Specific examples of the aliphatic and/or alicyclic dicarboxylic acidunit constituting the aliphatic polyester resin include succinic acidunit, oxalic acid unit, malonic acid unit, glutaric acid unit, adipicacid unit, pimelic acid unit, suberic acid unit, azelaic acid unit,sebacic acid unit, undecanedioic acid unit, dodecanedioic acid unit,1,4-cyclohexanedicarboxylic acid unit. These units may be used as amixture of two or more of them.

Specific examples of the aliphatic oxycarboxylic acid unit constitutingthe aliphatic oxycarboxylic acid resin include glycolic acid unit,lactic acid unit, 3-hydroxybutyric acid unit, 4-hydroxybutyric acidunit, 4-hydroxyvaleric acid unit, 5-hydroxyvaleric acid unit, and6-hydroxycaproic acid unit. These units may be used as a mixture of twoor more of them.

The aliphatic polyester resin may be copolymerized with an oxycarboxylicacid unit such as lactic acid unit or 6-hydroxycaproic acid unit. Theabove-described oxycarboxylic acid unit is used in an amount, as theupper limit, of typically 70 mole % or less, preferably 50 mole % orless, more preferably 30 mole % or less, most preferably 10 mole % orless based on 100 mole % of all the monomer units constituting thepolyester.

The aliphatic polyester resin may be copolymerized with a tri- or higherfunctional alcohol or carboxylic acid. More specifically, it may becopolymerized with a tri- or higher functional polyhydric alcohol,polycarboxylic acid or polyoxycarboxylic acid such astrimethylolpropane, glycerin, pentaerythritol, propanetricarboxylicacid, malic acid, citric acid, tartaric acid, hydroxyglutaric acid,hydroxymethylglutaric acid, hydroxyisophthalic acid orhydroxyterephthalic acid. With regard to the amount of the tri- orhigher functional compound unit which may be a cause for generation of agel, the upper limit is typically 5 mole % or less, preferably 1 mole %or less, more preferably 0.50 mole % or less, especially 0.3 mole % orless based on 100 mole % of all the monomer units constituting thepolyester. When a tri- or higher functional compound is used as acopolymerizable component for easily preparing a polyester having a highdegree of polymerization, the lower limit of its using amount that canbring about its effect is typically 0.0001 mole % or greater, preferably0.001 mole % or greater, more preferably 0.005 mole % or greater,especially preferably 0.01 mole % or greater. The aliphaticoxycarboxylic acid resin may be copolymerized with an aliphatic and/oralicyclic diol unit or an aliphatic and/or alicyclic dicarboxylic acidunit such as 1,4-butanediol unit, succinic acid unit or adipic acidunit; or a tri- or higher functional aliphatic polyhydric alcohol unit,aliphatic polycarboxylic acid unit or aliphatic polyoxycarboxylic acidunit such as trimethylolpropane unit, glycerin unit, pentaerythritolunit, propanetricarboxylic acid unit, malic acid unit, citric acid unit,or tartaric acid unit. The upper limit of the amount of theabove-described unit is typically 90 mole % or less, preferably 70 mole% or less, more preferably 50 mole % or less based on 100 mole % of allthe monomer units constituting the polyester.

The diol (polyhydric alcohol) unit, dicarboxylic acd (polycarboxylicacid) unit and oxycarboxylic acid unit constituting the aliphaticpolyester resin have an aliphatic compound unit as a main component, butthe aliphatic polyester resin may contain a small amount of anothercomponent, for example, an aromatic compound unit such as aromatic diol(polyhydric alcohol) unit, aromatic dicarboxylic acid (polycarboxylicacid) unit or aromatic oxycarboxylic acid unit without impairingbiodegradability of the resin. Specific examples of the aromatic diol(polyhydric alcohol) unit include bisphenol A unit and1,4-benzenedimethanol unit; those of the aromatic dicarboxylic acid(polycarboxylic acid) unit include terephthalic acid unit, isophthalicacid unit, trimellitic acid unit, pyromellitic acid unit,benzophenonetetracarboxylic acid unit, phenylsuccinic acid unit and1,4-phenylenediacetic acid unit; and those of the aromatic oxycarboxylicacid unit include hydroxybenzoic acid unit. The introduction amount ofthese aromatic compound units is 50 mole % or less, preferably 30 mole %or less based on the whole polymer.

No particular limitation is imposed on the production process of thealiphatic polyester resin and a publicly known manner can be employed.An urethane bond, amide bond, carbonate bond, ether bond, ketone bond orthe like may be introduced into the aliphatic polyester resin withoutadversely affecting the biodegradability thereof. As the aliphaticpolyester, that having an increased molecular weight or beingcrosslinked by using, for example, an isocyanate compound, epoxycompound, oxazoline compound, acid anhydride, peroxide, or the like maybe used. Further, it may be sealed, at the end group thereof, with acarbodiimide, epoxy compound, monofunctional alcohol or carboxylic acid.

Examples of the polysaccharides include cellulose, modified cellulosesuch as cellulose acetate, chitin, chitosan, starch and modified starch.

Examples of the other biodegradable resin include polyvinyl alcohol,modified polyvinyl alcohol, and polyalkylene glycols such aspolyethylene glycol and polypropylene glycol.

Examples of the general-purpose thermoplastic resin include polyolefinresins such as polyethylene, polypropylene, ethylene-vinyl acetatecopolymer and ethylene-α-olefin copolymer, halogenated resins such aspolyvinyl chloride, polyvinylidene chloride, chlorinated polyolefin andpolyvinylidene fluoride; styrene resins such as polystyrene andacrylonitrile-butadiene-styrene copolymer, polyester resins such aspolyethylene terephthalate and polybutylene terephthalate; elastomerssuch as polyisoprene, polybutadiene, acrylonitrile-butadiene copolymerrubber, styrene-butadiene copolymer rubber and styrene-isoprenecopolymer rubber; polyamide resins such as nylon 66 and nylon 6; andpolyvinyl acetate, methacrylate resins, polycarbonate resins,polyacetal, polyphenylene oxide and polyurethane. Their variousproperties may be adjusted by using a compatibilizer agent incombination.

The mixing ratio (weight ratio) of the polyester of the presentinvention to the above-described resin in the polyester composition willbe described above specifically. The general mixing ratio, to be used incommon, of the polyester resin of the present invention to variousresins is preferably 99.9/0.1 or greater but not greater than 0.1/99.9,more preferably 99/1 or greater but not greater than 1/99, mostpreferably 98/2 or greater but not greater than 2/98.

The composition can also be obtained by adding various conventionallyknown additives.

The additives are those used for resins and examples include crystalnucleating agent, antioxidant, antiblocking agent, ultraviolet absorber,light stabilizer, plasticizer, heat stabilizer, colorant, flameretardant, release agent, antistatic, antifog agent, surface wetnessimprover, incineration assistant, pigment, lubricant, dispersing aid,and various surfactants. These additives are added typically in anamount of from 0.01 to 5 wt. % based on the total weight of thecomposition. These additives may be used either singly or as a mixtureof two or more of them.

The polyester composition is also available by incorporating variousconventionally-known fillers therein. As a functional additive, chemicalfertilizer, soil improver, plant activator or the like can also beadded. The fillers can be classified roughly into inorganic fillers andorganic fillers. They may be used either singly or as a mixture of twoor more of them.

Examples of the inorganic filler include anhydrous silica, mica, talc,titanium oxide, calcium carbonate, diatomaceous earth, allophone,bentonite, potassium titanate, zeolite, sepiolite, smectite, kaolin,kaolinite, glass, limestone, carbon, wollastonite, calcined pearlite,silicates such as calcium silicate and sodium silicate, aluminum oxide,magnesium carbonate, hydroxides such as calcium hydroxide, and saltssuch as ferric carbonate, zinc oxide, iron oxide, aluminum phosphate andbarium sulfate. The content of the inorganic filler is typically from 1to 80 wt. %, preferably from 3 to 70 wt. %, more preferably from 5 to 60wt. % based on the total weight of the composition. Some of theinorganic fillers, for example, calcium carbonate and limestone, haveproperties of a soil improver. If a biomass-resource-derived polyestercomposition containing a particularly large amount of theabove-described inorganic filler is discarded to soil, the inorganicfiller after biodegradation remains in the soil and functions as a soilimprover. The resulting composition has therefore increased significanceas green plastic. Usefulness of the polyester of the present inventioncan be enhanced by molding the polyester composition added with achemical fertilizer, soil improver, plant activator, or the like andusing the product thus obtained as a material to be discarded in thesoil such as agricultural material or civil engineering material.

Examples of the organic filler include native starch, modified starch,pulp, chitin.chitosan, coconut shell flour, wood powder, bamboo powder,bark powder, kenaf powder, and straw powder. These powders may be usedeither singly or as a mixture of two or more of them. The amount of theorganic filler is typically from 0.01 to 70 wt. % based on the totalweight of the composition. Particularly, the organic filler remains inthe soil and plays a role as a soil improver or fertilizer afterbiodegradation of the polyester composition so that it enhances the roleof the composition as green plastic.

To the production of the composition, any conventionally knownmixing/kneading technology can be applied. As a mixer, horizontalcylindrical type, V-shaped type and double conical type mixers, blenderssuch as ribbon blender and super mixer, and various continuous mixersare usable. As a kneader, batch kneaders such as roll and internalmixer, one-stage and two-stage continuous kneaders, twin screw extruderand single screw extruder are usable. Examples of the kneading methodinclude a method of melting the composition under heating, adding eachadditive, filler or thermoplastic resin to the molten composition, andkneading the mixture. A blending oil may be added in order to dispersethe various additives uniformly.

The polyester or composition thereof according to the present inventioncan be molded by various molding methods employed for general-purposeplastics. Examples include compression molding (compression molding,lamination molding, stampable molding), injection molding, extrusion orco-extrusion (film extrusion using inflation or T-die method,lamination, sheet extrusion, pipe extrusion, wire/cable extrusion,profile extrusion), hollow molding (blow molding of every kind),calendering, foam molding (melt foam molding, solid-phase foam molding),solid forming (uniaxial stretching, biaxial stretching, rolling,formation of oriented nonwoven cloth, thermoforming [vacuum forming,compression air forming, plastic forming), powder molding (rotationmolding), and nonwoven fabric forming (dry method, adhesion method,entanglement method, spunbond method, and the like).

The polyester or composition thereof according to the present inventionmay be subjected to secondary processing suited for various purposes inorder to impart it with surface functions such as chemical function,electrical function, magnetic function, mechanical function,friction/abrasion/lubrication function, optical function, thermalfunction or biocompatibility. Examples of the secondary processinginclude embossing, painting, adhesion, printing, metalizing (plating orthe like), mechanical processing, and surface treatment (antistatictreatment, corona discharge treatment, plasma treatment, photochromismtreatment, physical vapor deposition, chemical vapor deposition, coatingor the like).

By the above-described molding methods, various molded products such asmonolayer film, multilayer film, stretched film, shrink film, laminatefilm, monolayer sheet, multilayer sheet, stretched sheet, pipe,wire/cable, monofilament, multifilament, various nonwoven fabrics, flatyarn, staple, crimped fibers, stretched tape or band, striated tape,split yarn, composite fibers, blow bottle and foam. The molded productsthus obtained are expected to be used for shopping bags, garbage bags,various films such as agricultural films, various containers such ascosmetic containers, detergent containers, food container, andcontainers for bleaching agent, fishing lines, fish nets, ropes, bindingmaterials, surgical yarns, sanitary cover stock materials, coolingboxes, buffer materials, medical materials, electric appliancematerials, chassis for household electric appliances and automobilematerials.

EXAMPLES

The present invention will hereinafter be described more specifically.It should however be borne in mind that the present invention is notlimited to or by these Examples without departing from the scope of thepresent invention. The characteristic values in the following exampleswere measured by the following methods. The term ppm as used hereinmeans mass ppm.

Dilute solution viscosity (reduced viscosity): Polyester was dissolvedin phenol/tetrachloroethane (1/1 (mass ratio) mixture) so as to give itsconcentration of 0.5 g/dL and time t (sec) required for falling of theresulting solution through a viscosity tube in a temperature-controlledbath of 30° C. was measured. In addition, time t₀ (sec) required forfalling of the solvent alone was also measured at 30° C. and a reducedviscosity η_(sp)/C (=(t−t₀)/t₀·C) was calculated (C represents theconcentration of the solution).

Nitrogen atom content: 10 mg of a sample was weighed on a quartz boat.It was burnt using a total nitrogen analyzer (TN-10, product ofMitsubishi Chemical) and a nitrogen atom content of it was determined bychemiluminescence.

Sulfur atom content: About 0.1 g of a sample was weighed on a platinumboat. It was burned in a quartz tubular furnace AQF-100 (concentrationsystem) (product of Mitsubishi Chemical). A sulfur content in thecombustion gas was caused to absorb by a 0.1% aqueous solution ofhydrogen peroxide. The sulfate ion in the resulting solution was thenmeasured using ion chromatography (ICS-1000, product of Dionex).

Water containing amount (water content): After water was evaporated from0.5 g of a sample by heating and melting at 200° C. in a moisturevaporizer (VA-200, product of Mitsubishi Chemical), a total watercontent thus evaporated was determined in accordance the coulometrictitration based on the principle of Karl Fischer reaction by using atrace moisture meter (CA-100, product of Mitsubishi Chemical).

Amount of terminal carboxyl groups: It was determined by dissolving theresulting polyester in benzyl alcohol, followed by titration with 0.1NNaOH. It was a carboxyl equivalent per 1×10⁶ g.

YI: It was determined in accordance with the method of JIS K7105.

Referential Example 1 <Construction of Gene Disruption Vector>

(A) Extraction of Bacillus subtilis Genomic DNA

Bacillus subtilis (ISW1214) was cultured in 10 mL of an LS medium[composition: obtained by dissolving 10 g of tryptone, 5 g of yeastextract and 5 g of NaCl in 1 L of distilled water] until a latelogarithmic growth phase and bacterial cells thus grown were collected.The resulting bacterial cells were suspended in 0.15 mL of a solutioncontaining a 10 mM NaCl/20 mM Tris buffer (pH 8.0)/1 mM EDTA.2Nasolution containing lysozyme to give its concentration of 10 mg/mL.

Next, Proteinase K was added to the resulting suspension to give itsfinal concentration of 100 μg/mL and the resulting mixture was kept at37° C. for 1 hour. Sodium dodecyl sulfate solution was then added togive its final concentration of 0.5% and the mixture was kept at 50° C.for 6 hours to cause bacteriolysis. After addition of an equal amount ofphenol/chloroform solution to the resulting lysate solution and mildshaking at room temperature for 10 minutes, the whole amount of themixture was centrifuged (5,000×g, 20 minutes, from 10 to 12° C.). Thesupernatant fraction was collected and sodium acetate solution was addedto the supernatant fraction at a concentration of 0.3M. To the resultingmixture was added two times the amount of ethanol, followed by mixing.The precipitate obtained by centrifugation (15,000×g, 2 minutes) waswashed with 70% ethanol, and then air-dried. To the resulting DNA wasadded 5 mL of a 10 mM tris buffer (pH 7.5)-1 mM EDTA.2Na solution. Theresulting mixture was allowed to stand overnight at 4° C. and then, usedas a template DNA for PCR performed later.

(B) Amplification and Cloning of SacB Gene by PCR

A Bacillus subtilis SacB gene was obtained by performing PCR using theDNA prepared in the above (A) as a template and synthetic DNAs (SEQ IDNO: 1 and SEQ ID NO: 2) designed based on the nucleotide sequence of thegene (GenBank Database Accession No. X02730) which had already beenreported.

Composition of reaction liquid: 1 μL of the template DNA, 0.2 μL ofPfxDNA polymerase (product of Invitrogen), 1-fold concentration of asupplied buffer, 0.3 μM of each of primers, 1 mM MgSO₄, and 0.25 μMdNTPs were mixed to give a total volume of 20 μL.

Reaction temperature condition: DNA Thermal Cycler PTC-200 (product ofMJ Research) was used and a cycle composed of 94° C. for 20 seconds and68° C. for 2 minutes was repeated for 35 times. Heat retention at 94° C.at the first cycle was conducted for 1 minute and 20 seconds, while heatretention at 68° C. at the last cycle was conducted for 5 minutes.

Confirmation of the amplified product was performed by separation by0.75% agarose (SeaKem GTG agarose: product of FMC BioProducts) gelelectrophoresis, followed by visualization with ethidium bromidestaining, whereby a fragment of about 2 kb was detected. The target DNAfragment was recovered from the gel by using QIAQuick Gel Extraction Kit(product of QIAGEN).

After phosphorylation of the 5′-end of the recovered DNA fragment withT4 Polynucleotide Kinase (product of Takara Shuzo), the resultingfragment was inserted into the EcoRV site of an Escherichia coli vector(pBluescript II, product of STRATEGENE) by using Ligation Kit ver. 2(product of Takara Shuzo), and with the plasmid DNA thus obtained,Escherichia coli (DH5α strain) was transformed. The recombinantEscherichia coli obtained in such a manner was smeared onto an LB agarmedium [obtained by dissolving 10 g of tryptone, 5 g of yeast extract, 5g of NaCl, and 15 g of agar in 1 L of distilled water] containing 50μg/mL ampicillin and 50 μg/mL X-Gal.

Clones which had formed a white colony on the medium were transferred toan LB agar medium containing 50 μg/mL ampicillin and 10% sucrose andwere cultured at 37° C. for 24 hours. Of those clones, those whichfailed to grow on the medium containing sucrose were subjected to liquidculture in a conventional manner, followed by the formation of theplasmid DNA. A strain permitting functional expression of an SacB genein Escherichia coli must be incapable of growing in thesucrose-containing medium. The plasmid DNA thus obtained was digestedwith restriction enzymes SalI and PstI. The plasmid DNA thus obtainedwas confirmed to have an inserted fragment of about 2 kb and the plasmidwas named pBS/SacB.

(C) Construction of Chloramphenicol-Resistant SacB Vector

500 ng of Escherichia coli plasmid vector pHSG396 (Chloramphenicolresistant marker, product of Takara Shuzo) was reacted with 10 units ofrestriction enzyme PshBI at 37° C. for 1 hour, followed by recovery byphenol/chloroform extraction and ethanol precipitation. After bluntingof the both ends with Klenow Fragment (product of Takara Shuzo),ligation with MluI linker (product of Takara Shuzo) by using LigationKit ver. 2 (product of Takara Shuzo) and circularization, Escherichiacoli (DH5α strain) was transformed. The recombinant Escherichia colithus obtained was smeared onto an LB agar medium containing 34 μg/mLchloramphenicol. A plasmid DNA was isolated from the resulting clones ina conventional manner. A clone having a cleavage site of a restrictionenzyme MluI was selected and named pHSG396Mlu.

On the other hand, pBS/SacB thus constructed in the above (B) wasdigested with restriction enzymes SalI and PstI and then, the both endsthereof were blunted with the Klenow Fragment. The MluI linker wasligated by using Ligation Kit ver. 2 (product of Takara Shuzo). A DNAfragment of about 2.0 kb containing a SacB gene was then separated by0.75% agarose gel electrophoresis and then, recovered. The resultingSacB gene fragment was ligated to the pHSG396Mlu fragment, which hadbeen digested with restriction enzyme MluI and then dephosphorylated, atthe end of the fragment, with Alkaline Phosphatase Calf intestine(product of Takara Shuzo), by using Ligation Kit ver. 2 (product ofTakara Shuzo), whereby Escherichia coli (DH5α strain) was transformed.The recombinant Escherichia coli thus obtained was smeared onto an LBagar medium containing 34 μg/mL chloramphenicol. The colonies thusobtained were transferred to an LB agar medium containing 34 μg/mLchloramphenicol and 10% sucrose, and cultured at 37° C. for 24 hours.Plasmid DNA was isolated in a conventional manner from the clones whichhad failed to grow on the sucrose-containing medium among these clones.The plasmid DNA thus obtained was analyzed by digestion with MluI. As aresult, the plasmid DNA was confirmed to have an inserted fragment ofabout 2.0 kb and it was named pCMB1.

(D) Acquisition of Kanamycin-Resistant Gene

A kanamycin-resistant gene was obtained by PCR using a DNA ofEscherichia coli plasmid vector pHSG299 (kanamycin resistant marker:product of Takara Shuzo) as a template and synthetic DNAs shown in SEQID NO: 3 and SEQ ID NO: 4 as primers.

Composition of reaction liquid: 1 ng of the template DNA, 0.1 μL ofPyrobest DNA polymerase (product of Takara Shuzo) 1-fold concentrationof a supplied buffer, 0.5 μM of each primer, and 0.25 μM dNTPs weremixed to give a total amount of 20 μL.

Reaction temperature condition: DNA Thermal Cycler PTC-200 (product ofMJ Research) was used and a cycle composed of 94° C. for 20 seconds, 62°C. for 15 seconds, and 72° C. for 1 minute and 20 seconds was repeated20 times. Heat retention at 94° C. at the first cycle was conducted for1 minute and 20 seconds, while heat retention at 72° C. at the lastcycle was conducted for 5 minutes.

Confirmation of the amplified product was performed by separation by0.75% agarose (SeaKem GTG agarose: product of FMC BioProducts) gelelectrophoresis, followed by visualization with ethidium bromidestaining, whereby a fragment of about 1.1 kb was detected. The targetDNA fragment was recovered from the gel by using QIAQuick Gel ExtractionKit (product of QIAGEN). A 5′-end of the DNA fragment thus recovered wasphosphorylated with T4 Polynucleotide Kinase (product of Takara Shuzo).

(E) Construction of Kanamycin-Resistant SacB Vector

A DNA fragment of about 3.5 kb obtained by digesting, with restrictionenzymes Van91I and ScaI, the pCMB1 constructed in the above (C) wasseparated by 0.75% agarose gel electrophoresis and, then recovered. Theresulting DNA fragment was mixed with the kanamycin resistant geneprepared in the above (D) and ligated thereto by using Ligation Kit ver.2 (product of Takara Shuzo). With the plasmid DNA thus obtained,Escherichia coli (DH5α strain) was transformed. The recombinantEscherichia coli thus obtained was smeared onto an LB agar mediumcontaining 50 μg/mL kanamycin.

It was confirmed that the strain grown on the kanamycin-containingmedium had failed to grow on the sucrose-containing medium. The plasmidDNA prepared from the strain was digested with restriction enzymeHindIII to generate Fragments of 354, 473, 1807, and 1997 bp, suggestingthat the plasmid DNA definitely had a structure as illustrated inFIG. 1. The plasmid was named pKMB1.

Reference Example 2 <Construction of LDH Gene Disrupted Strain>

(A) Extraction of Genomic DNA from Brevibacterium flavum MJ233-ES Strain

A Brevibacterium flavum MJ-233 strain was cultured until a latelogarithmic growth phase in 10 mL of medium A (obtained by dissolving 2g of urea, 7 g of (NH₄)₂SO₄, 0.5 g of KH₂PO₄, 0.5 g of K₂HPO₄, 0.5 g ofMgSO₄.7H₂O, 6 mg of FeSO₄.7H₂O, 6 mg of MnSO₄.4-5H₂O, 200 μg of biotin,100 μg of thiamine, 1 g of yeast extract, 1 g of casamino aid, and 20 gof glucose in 1 L of distilled water). A genomic DNA was prepared usingthe cells thus obtained by the method as described above in (A) ofReferential Example 1.

(B) Cloning of Lactate Dehydrogenase Gene

A lactate dehydrogenase gene of MJ233 strain was obtained by PCR usingthe DNA prepared in the above (A) as a template and synthetic DNAs (SEQID NO: 5 and SEQ ID NO:6) designed based on the nucleotide sequence ofthe gene described in Japanese Patent Laid-Open No. Hei 11-206385.

Composition of reaction liquid: 1 μL of the template DNA, 0.2 μL ofTaqDNA polymerase (product of Takara Shuzo), 1-fold concentration of anattached buffer, 0.2 μM of each primer, and 0.25 μM of dNTPs were mixedto give a total amount of 20 μL.

Reaction temperature condition: By using DNA Thermal Cycler PTC-200(product of MJ Research), a cycle composed of 94° C. for 20 seconds, 55°C. for 20 seconds, and 72° C. for 1 minute was repeated 30 times. Heatretention at 94° C. at the first cycle was conducted for 1 minute and 20seconds, while heat retention at 72° C. at the last cycle was conductedfor 5 minutes.

Confirmation of the amplified product was performed by separation by0.75% agarose (SeaKem GTG agarose: product of FMC BioProducts) gelelectrophoresis and visualization with ethidium bromide staining,whereby a fragment of about 0.95 kb was detected. The target DNAfragment was recovered from the gel by using QIAQuick Gel Extraction Kit(product of QIAGEN).

The DNA fragment thus recovered was mixed with a PCR product cloningvector pGEM-TEasy (product of Promega) and ligated thereto usingLigation Kit ver. 2 (product of Takara Shuzo). Escherichia coli (DH5αstrain) was then transformed using the resulting plasmid DNA. Therecombinant Escherichia coli thus obtained was smeared onto an LB agarmedium containing 50 μg/mL ampicillin and 50 μg/mL X-Gal.

Clones which had formed a white colony on the medium were subjected toliquid culture in a conventional manner, and then the plasmid DNA waspurified. The resulting plasmid DNA was digested with restrictionenzymes SacI and SphI, whereby an inserted fragment of about 1.0 kb wasrecognized and it was named pGEMT/CgLDH.

(C) Construction of Plasmid for Disrupting Lactate Dehydrogenase Gene

By digestion of the pGEMT/CgLDH prepared in the above (B) withrestriction enzymes EcoRV and XbaI, a coding region of lactatedehydrogenase of about 0.25 kb was cut out. By blunting the end of theremaining DNA fragment of about 3.7 kb by the Klenow Fragment andcircularizing it using Ligation Kit ver. 2 (product of Takara Shuzo),Escherichia coli (DH5α strain) was transformed. The recombinantEscherichia coli thus obtained was smeared onto an LB agar mediumcontaining 50 μg/mL ampicillin. The strain grown on the medium wassubjected to liquid culture in a conventional manner, and then theplasmid DNA was purified. The resulting plasmid DNA was digested withrestriction enzymes SacI and SphI. A clone which was recognized to havean inserted fragment of about 0.75 kb was selected and it was namedpGEMT/ΔLDH.

Next, the DNA fragment of about 0.75 kb obtained by digesting thepGEMT/ΔLDH with the restriction enzymes SacI and SphI was separated by0.75% agarose gel electrophoresis and recovered to prepare a lactatedehydrogenase gene fragment containing a defective region. The resultingDNA fragment was mixed with the pKMB1 constructed in Referential Example1 by digestion with the restriction enzymes SacI and SphI, and ligatedthereto by using Ligation Kit ver. 2 (product of Takara Shuzo). With theplasmid DNA thus obtained, Escherichia coli (DH5α strain) wastransformed. The recombinant Escherichia coli thus obtained was smearedonto an LB agar medium containing 50 μg/mL of kanamycin and 50 μg/mL ofX-Gal.

After clones which had formed a white colony on the medium weresubjected to liquid culture in a conventional manner, the plasmid DNAwas purified. By digesting the plasmid DNA thus obtained withrestriction enzymes SacI and SphI, a clone having an inserted fragmentof about 0.75 kb was selected and named pKMB1/ΔLDH (FIG. 2).

(D) Construction of Lactate Dehydrogenase Gene-Disrupted Strain Derivedfrom Brevibacterium flavum MJ233-ES Strain

A plasmid DNA to be used for transformation of the Brevibacterium flavumMJ-233 strain was prepared from an Escherichia coli JM110 straintransformed with pKMB1/ΔLDH by a calcium chloride method (Journal ofMolecular Biology, 53, 159, 1970).

The transformation of the Brevibacterium flavum MJ233-ES strain wasperformed by an electric pulse method (Res. Microbiol., Vol. 144, p.181-185, 1993), and the resulting transformant was smeared onto an LBGagar medium [obtained by dissolving 10 g of tryptone, 5 g of yeastextract, 5 g of NaCl, 20 g of glucose, and 15 g of agar in 1 L ofdistilled water) containing 50 μg/mL kanamycin.

Since pKMB1/ΔLDH was an unreplicable plasmid in the Brevibacteriumflavum MJ233-ES strain, homologous recombination was caused between alactate dehydrogenase gene on the plasmid and the same gene on thegenome of the Brevibacterium flavum MJ-233 strain. As a result, thestrain grown on the above-described medium must have, on the genomethereof, a kanamycin-resistant gene and SacB gene derived from theplasmid.

Next, the strain obtained by homologous recombination was subjected toliquid culture on an LBG medium containing 50 μg/mL kanamycin. Theculture solution corresponding to about 1000000 cells was smeared ontoan LBG medium containing 10% sucrose. As a result, about 10 strainswhich were presumed to be sucrose-insensitive as a result of loss of theSacB gene caused by the second homologous recombination were obtained.

The strains thus obtained include a strain in which the lactatedehydrogenase gene has been replaced by a mutation type derived frompKMB1/ΔLDH and a strain in which the lactate dehydrogenase gene has beenreverted to a wild type. Whether the lactate dehydrogenase gene is amutation type or a wild type can be confirmed easily by subjecting acell obtained by liquid culture in an LBG medium to direct PCR anddetecting the lactate dehydrogenase gene. Analysis of the lactatedehydrogenase gene by using PCR amplification primers (SEQ ID NO: 7 andSEQ ID NO:8) may reveal that the wild type has a DNA fragment of 720 bpand a mutation type having a depletion region has a DNA fragment of 471bp.

As a result of analysis of the sucrose-insensitive strain by theabove-mentioned method, a strain having only a mutation type gene wasselected and the strain was named Brevibacterium flavum MJ233/ΔLDH.

(E) Confirmation of Lactate Dehydrogenase Activity

Brevibacterium flavum MJ233/ΔLDH strain prepared by the above (D) wasinoculated into medium A and then aerobically cultured at 30° C. for 15hours with shaking. The resulting culture was centrifuged (3,000×g, 4°C. for 20 minutes). The cells were collected and then, washed with asodium-phosphate buffer [composition: 50 mM sodium phosphate buffer (pH7.3)).

Then, 0.5 g (wet weight) of the washed cells was suspended in 2 mL ofthe sodium-phosphate buffer. The resulting suspension was subjected to aultrasonicator (product of Branson) while ice cooling, whereby celldebris was obtained. The resulting cell debris was centrifuged(10,000×g, 4° C. for 30 minutes) and the supernatant was then obtainedas a crude enzyme solution. Similarly, a crude enzyme solution ofBrevibacterium flavum MJ233-ES strain was prepared as a control and thensubjected to the following activity measurement.

The enzymatic activity of lactate dehydrogenase was confirmed bymeasuring, as a change in absorbance at 340 nm, oxidation of coenzymeNADH to NAD⁺ caused by lactic acid generated using pyruvic acid as asubstrate [L. Kanarek and R. L. Hill, J. Biol. Chem. 239, 4202 (1964)].The reaction was effected at 37° C. in the presence of 50 mMpotassium-phosphate buffer (pH 7.2), 10 mM pyruvic acid and 0.4 mM NADH.Consequently, the lactate dehydrogenase activity of the crude enzymesolution prepared from Brevibacterium flavum MJ233/ΔLDH strain was onetenth or less of the lactate dehydrogenase activity of the crude enzymesolution prepared from Brevibacterium flavum MJ233-ES strain.

Referential Example 3 Construction of Coryneform bacteria ExpressionVector

(A) Preparation of Promoter Fragment for Coryneform bacteria

A DNA fragment (which will hereinafter be called TZ4 promoter) ofcoryneform bacteria shown in SEQ ID NO: 4 in Japanese Patent Laid-OpenNo. Hei 7-95891 and reported to have high promoter activity was used.The promoter fragment was obtained by PCR using the Brevibacteriumflavum MJ233 genomic DNA prepared in (A) of Referential Example 2 as atemplate and synthetic DNAs (SEQ ID NO: 9 and SEQ ID NO: 10) designedbased on a sequence described as SEQ ID NO: 4 in Japanese PatentLaid-Open No. Hei 7-95891.

Composition of reaction liquid: 1 μL of the template DNA, 0.2 μL ofPfxDNA polymerase (product of Invitrogen Japan) 1-fold concentration ofan attached buffer, 0.3 μM of each primer, 1 mM of MgSO₄, and 0.25 μMdNTPs were mixed to give a total volume of 20 μL.

Reaction temperature condition: DNA Thermal Cycler PTC-200 (product ofMJ Research) was used and a cycle composed of 94° C. for 20 seconds, 60°C. for 20 seconds, and 72° C. for 30 seconds was repeated 35 times. Heatretention at 94° C. at the first cycle was conducted for 1 minute and 20seconds while heat retention at 72° C. at the final cycle was conductedfor 2 minutes.

Confirmation of the amplified product was performed by separation by2.0% agarose (SeaKem GTG agarose: product of FMC BioProducts) gelelectrophoresis and visualization with ethidium bromide staining,whereby a fragment of about 0.25 kb was detected. The target DNAfragment was recovered from the gel by using QIAQuick Gel Extraction Kit(product of QIAGEN).

The 5′-end of the recovered DNA fragment was phosphorylated with T4Polynucleotide Kinase (product of Takara Shuzo) and was ligated to anSmaI site of an Escherichia coli vector pUC 19 (Takara Shuzo) by usingLigation Kit ver. 2 (product of Takara Shuzo). With the plasmid DNA thusobtained, Escherichia coli (DH5α strain) was transformed. The resultingrecombinant Escherichia coli was smeared onto an LB agar mediumcontaining 50 μg/mL ampicillin and 50 μg/mL X-Gal.

After six clones which had formed a white colony on the resulting mediumwere subjected to liquid culture in a conventional manner, the plasmidsDNA were purified and the base sequences thereof were determined,respectively. A clone having a TZ4 promoter inserted therein so as tohave transcription activity in a direction opposite to the lac promoteron pUC 19 was selected from them and it was named pUC/TZ4.

Next, a DNA linker composed of synthetic DNAs (SEQ ID NO; 11 and SEQ IDNO; 12) each having a phosphorylated 5′-end and having, at both ends,cohesive ends corresponding to BamHI and PstI was mixed with the DNAfragment prepared by digesting the pUC/TZ4 with restriction enzymesBamHI and PstI to ligate them each other by using Ligation Kit ver. 2(product of Takara Shuzo). With the plasmid DNA thus obtained,Escherichia coli (DH5α strain) was transformed. The above-described DNAlinker includes a ribosome binding sequence (AGGAGG) and a cloning site(PacI, NotI, and ApaI arranged in this order from upstream) downstreamof the ribosome binding sequence.

Clones which had formed a white colony on the medium were subjected toliquid culture in a conventional manner, and then the plasmids DNA werepurified, respectively. A plasmid DNA capable of being digested withrestriction enzyme NotI was selected from the plasmids DNA thus obtainedand it was named pUC/TZ4-SD.

A promoter fragment of about 0.3 kb obtained by digesting the pUC/TZ4-SDthus constructed with a restriction enzyme PstI, blunted at the endthereof with the Klenow Fragment, and digested with restriction enzymeKpnI was separated by 2.0% agarose gel electrophoresis and then,recovered.

(B) Construction of Expression Vector for Coryneform bacteria

pHSG298par-rep described in Japanese Patent Laid-Open No. Hei 12-93183was used as a plasmid replicable autonomously and stably in coryneformbacteria. The plasmid is equipped with a replication region and astabilization-function-having region of a natural plasmid pBY503 thatBrevibacterium stationis IF012144 strain possesses, and a kanamycinresistant gene and a replication region of Escherichia coli derived fromEscherichia coli vector pHSG298 (Takara Shuzo). DNA prepared bydigesting the pHSG298par-rep with a restriction enzyme SseI, bluntingits ends with the Klenow Fragment, and digesting it with a restrictionenzyme KpnI was mixed with the TZ4 promoter fragment prepared in theabove (A) and ligated thereto by using Ligation Kit ver. 2 (product ofTakara Shuzo). With the plasmid DNA thus obtained, Escherichia coli(DH5α strain) was transformed. The resulting recombinant Escherichiacoli was smeared onto an LB agar medium containing 50 μg/mL kanamycin.

After the strains grown on the resulting medium were subjected to liquidculture in a conventional manner, the plasmid DNAs were purified. Of theplasmid DNAs, a plasmid DNA capable of being digested with restrictionenzyme NotI was selected and it was named pTZ4 (FIG. 3 shows theconstruction procedure).

Referential Example 4 Construction of Pyruvate CarboxylaseActivity-Enhanced Strain (A) Acquisition of Pyruvate Carboxylase Gene

A pyruvate carboxylase gene derived from the Brevibacterium flavum MJ233strain was obtained by PCR using the DNA prepared in the above (A) ofReferential Example 2 as a template and synthetic DNAs (SEQ ID NO: 13and SEQ ID NO: 14) designed based on the sequence (GenBank DatabaseAccession No. AP005276) of the pyruvate carboxylase gene of aCorynebacterium glutamicum ATCC 13032 strain whose entire genomicsequence had been reported.

Composition of reaction liquid: 1 μL of the template DNA, 0.2 μL ofPfxDNA polymerase (product of Invitrogen), 1-fold concentration of anattached buffer, 0.3 μM of each primer, 1 mM MgSO₄, and 0.25 μM dNTPswere mixed to give a total volume of 20 μL.

Reaction temperature condition: DNA Thermal Cycler PTC-200 (product ofMJ Research) was used and a cycle composed of 94° C. for 20 seconds and68° C. for 4 minutes was repeated 35 times. Heat retention at 94° C. atthe first cycle was conducted for 1 minute and 20 seconds, while heatretention at 68° C. at the final cycle was conducted for 10 minutes.After completion of PCR reaction, 0.1 μL of Takara Ex Taq (Takara Shuzo)was added and the mixture was kept further at 72° C. for 30 minutes.

Confirmation of the amplified product was performed by separation by0.75% agarose (SeaKem GTG agarose: product of FMC BioProducts) gelelectrophoresis and visualization with ethidium bromide staining,whereby a fragment of about 3.7 kb was detected. The target DNA fragmentwas recovered from the gel by using QIAQuick Gel Extraction Kit (productof QIAGEN).

The DNA fragment thus recovered was mixed with PCR product-cloningvector pGEM-TEasy (product of Promega) and ligated thereto usingLigation Kit ver. 2 (product of Takara Shuzo). Escherichia coli (DH5αstrain) was then transformed using the resulting plasmid DNA. Therecombinant Escherichia coli thus obtained was smeared onto an LB agarmedium containing 50 μg/mL ampicillin and 50 μg/mL X-Gal.

After the clone which had formed a white colony on the medium wassubjected to liquid culture in a conventional manner, the plasmid DNAwas purified. The resulting plasmid DNA was digested with restrictionenzymes PacI and ApaI, whereby an inserted fragment of about 3.7 kb wasrecognized and it was named pGEM/MJPC.

A base sequence of the inserted fragment in pGEM/MJPC was determined byusing the base sequencing device (model 377 XL) and BigDye TerminatorCycle Sequencing Kit ver. 3, each, product of Applied Biosystems. Thebase sequence thus obtained and a predicted amino acid sequence aredescribed in SEQ. ID NO: 15 and only the amino acid sequence is shown inSEQ. ID NO: 16. The amino acid sequence showed a very high homology(99.4%) to that derived from the Corynebacterium glutamicum ATCC 13032strain so that it was concluded that the pGEM/MJPC insert fragment was apyruvate carboxylase gene derived from the Brevibacterium flavum MJ233strain.

(B) Construction of Plasmid for Enhancing Pyruvate Carboxylase Activity

The pyruvate carboxylase gene fragment of about 3.7 kb obtained bydigesting the pGEM/MJPC, which had been prepared in the above (A), withthe restriction enzymes PacI and ApaI was separated by 0.75% agarose gelelectrophoresis and then, recovered.

The resulting DNA fragment was mixed with pTZ4, which had beenconstruted by digestion with restriction enzymes Pad and Apal inReferential Example 3, and ligated thereto by using Ligation Kit ver. 2(product of Takara Shuzo). With the plasmid DNA thus obtained,Escherichia coli (DH5α strain) was transformed. The resultingrecombinant Escherichia coli was smeared onto an LB agar mediumcontaining 50 μg/mL kanamycin.

After the strains grown on the medium were subjected to liquid culturein a conventional manner, the plasmid DNA was purified. The plasmid DNAthus obtained was digested with restriction enzymes PacI and ApaI. Aplasmid having an inserted fragment of about 3.7 kb was selected andnamed pMJPC1 (FIG. 4).

(C) Transformation to Brevibacterium flavum MJ233/ΔLDH Strain

A plasmid DNA replicable in the Brevibacterium flavum MJ233 strain andused for transformation by pMJPC1 was prepared from the Escherichia coli(DH5α strain) transformed in the above (B).

The transformation to a Brevibacterium flavum MJ233/ΔLDH strain wasperformed by the electric pulse method (Res. Microbiol., Vol. 144, p.181-185, 1993). The transformant thus obtained was smeared onto an LBGagar medium [obtained by dissolving 10 g of tryptone, 5 g of yeastextract, 5 g of NaCl, 20 g of glucose, and 15 g of agar in 1 L ofdistilled water] containing 50 μg/mL kanamycin.

After the strain which had grown on the medium was subjected to liquidculture in a conventional manner, a plasmid DNA was extracted. As aresult of analysis by digestion with a restriction enzyme, it wasconfirmed that the strain retained pMJPC1, and the strain was namedBrevibacterium flavum MJ233/PC/ΔLDH strain.

(D) Pyruvate Carboxylase Enzymatic Activity

The transformant strain Brevibacterium flavum MJ233/PC/ΔLDH obtained inthe above (C) was cultured overnight in 100 ml of medium A containing 2%glucose and 25 mg/l kanamycin. After harvesting of the cells thusobtained, they were washed with 50 ml of 50 mM potassium phosphatebuffer (pH 7.5), followed by re-suspension in 20 ml of a buffer having asimilar composition thereto. The suspension was subjected to sonicationwith SONIFIER 350 (product of Branson) and the centrifuged supernatantwas then provided as a cell-free extract. The pyruvate carboxylaseactivity was determined using the resulting cell-free extract. Themeasurement of enzymatic activity was carried out by allowing the enzymeto react at 25° C. in a reaction solution containing 100 mM Tris/HCLbuffer (pH 7.5), 0.1 mg/10 ml biotin, 5 mM magnesium chloride, 50 mMsodium hydrogen carbonate, 5 mM sodium pyruvate, 5 mM adenosinetriphosphate sodium, 0.32 mM NADH, 20 units/1.5 ml malate dehydrogenase(product of WAKO, originated from yeast). One unit (1 U) was defined asthe amount of enzyme for catalyzing a decrease of 1 μmol of NADH perminute. The specific activity in the cell-free extract in which pyruvatecarboxylase had been expressed was 0.2 U/mg of protein. On the otherhand, from the cells prepared similarly by incubating the parentMJ233/ΔLDH strain by using medium A, no pyruvate carboxylase activitywas detected by the activity measurement method.

Referential Example 5 <Preparation of Fermentation Liquid>

100 mL of a medium having a composition of 4 g of urea, 14 g of ammoniumsulfate, 0.5 g of monobasic potassium phosphate, 0.5 g of dibasicpotassium phosphate, 0.5 g of magnesium sulfate.7 hydrate, 20 mg offerrous sulfate.7 hydrate, 20 mg of manganese sulfate.hydrate, 200 μg ofD-biotin, 200 μg of thiamin hydrochloride, 1 g of yeast extract, 1 g ofcasamino acid, and 1000 ml of distilled water was charged in a 500-mLconical flask and then sterilized by heating at 120° C. for 20 minutes.The resulting medium was cooled to room temperature, followed by theaddition thereto of 4 mL of a 50% aqueous glucose solution sterilized inadvance and 50 μL of a 5% kanamycin solution subjected to asepticfiltration. The Brevibacterium flavum MJ233/PC/ΔLDH strain prepared inReferential Example 4 (C) was inoculated to the resulting medium andseed culture was carried out at 30° C. for 24 hours.

A medium containing 12 g of urea, 42 g of ammonium sulfate, 1.5 g ofmonobasic potassium phosphate, 1.5 g of dibasic potassium phosphate, 1.5g of magnesium sulfate.7 hydrate, 60 mg of ferrous sulfate.7 hydrate, 60mg of manganese sulfate.hydrate, 600 μg of D-biotin, 600 μg of thiaminhydrochloride, 3 g of yeast extract, 3 g of casamino acid, 1 ml ofantifoaming agent (Adecanol LG294: product of Asahi Denka), and 2500 mLof distilled water was charged in a 5-L fermenter, and sterilized byheating at 120° C. for 20 minutes. After cooling to room temperature,500 mL of a 12% aqueous glucose solution sterilized in advance wasadded. To the resulting mixture was added the whole amount of the seedculture solution obtained above and the mixture was kept at 30° C. Themain culture was carried out with aeration at a rate of 500 mL perminute and agitation at a rate of 500 rpm. After 12 hours, the glucosewas consumed almost completely.

A 3-L conical flask was charged with a medium containing 1.5 g ofmagnesium sulfate.7 hydrate, 60 mg of ferrous sulfate.7 hydrate, 60 mgof manganese sulfate.hydrate, 600 μg of D-biotin, 600 μg of thiaminhydrochloride, 5 ml of antifoaming agent (Adecanol LG294: product ofAsahi Denka), and 1.5 L of distilled water. The resulting medium wassterilized by heating at 120° C. for 20 minutes. After cooling to roomtemperature, cells collected by centrifugal separation, at 10000×g for 5minutes, of the culture solution obtained by the above-described mainculture were added to the resulting medium, followed by re-suspension togive its O.D. (660 nm) of 60. In a 5-L jar fermenter, 1.5 L of theresulting suspension and 1.5 L of a 20% glucose solution sterilized inadvance were charged and mixed. The resulting mixture was kept at 35° C.The reaction was effected while maintaining the pH at 7.6 with 2Mammonium carbonate, aerating at 500 mL/min and stirring at 300 rpm.Almost all the amount of glucose was consumed about 50 hours after thereaction was started. Accumulation of 57 g/L of succinic acid wasobserved. The resulting fermentation liquid was separated into cells andsupernatant by centrifugal separation at 10000×g for 5 minutes andultrafiltration (NTU-3000-C1R, product of Nitto Denko). Theabove-described operation was performed 30 times to yield 103 L of asupernatant of a succinic acid fermentation liquid.

<Purification of Succinic Acid from Succinic Acid Fermentation Liquid>

The supernatant of a succinic acid fermentation liquid (103 L, succinicacid content: 5.87 kg) obtained as described above was concentrated in ajacketted agitation tank under reduced pressure, whereby 17.8 kg(calculated value) of a concentrate having a succinic acid concentrationof 32.9% and ammonia concentration of 11.9% was obtained. To theresulting concentrate was added 8.58 kg of acetic acid (product ofDaicel Chemical) and the resulting mixture was cooled to 30° C. To thereaction mixture, was added 4.0 kg of methanol (product of KishidaChemical), followed by cooling to 15° C. After stirring for one hour,stirring was continued for 4 hours at 20° C.

Crystals thus precipitated were filtered through a centrifugal filter toyield 4.95 kg of crystals containing 74.61 of succinic acid, 3.5% ofacetic acid and 12.2% of ammonia.

To 11.3 kg of acetic acid was added 4.9 kg of the resulting crystals andthe latter was dissolved in the former at 85° C. The resulting solutionwas then cooled immediately to 20° C. The crystals had alreadyprecipitated, but stirring was continued for further 3 hours and thenfiltration was conducted through a centrifugal filter, whereby 2.44 kgof crystals containing 87.9% of succinic acid, 8.4% of acetic acid and0.6% of ammonia were obtained.

The resulting crystals were washed with 3.5 L of demineralized watercooled to 5° C. while sprinkling it to them. Filtration of them througha centrifugal filter yielded 2.08 kg of crystals containing 90% ofsuccinic acid, 1.7% of acetic acid, and 0.05% (about 500 ppm) ofammonia.

In 28.5 L of demineralized water, 2.0 kg of the resulting crude succinicacid crystals were dissolved and the resulting solution was caused topass through a tower filled with 1 L of an ion exchange resin (SK1BH,product of Mitsubishi Chemical) at SV=2, whereby about 33 L of a treatedsolution was obtained. The resulting solution was concentrated to about5.2 L while continuously feeding it to a rotary evaporator under reducedpressure. Crystals had already been precipitated at that stage. Afterthe concentrate was cooled to 5° C. and stirring was continued for 2hours, the reaction mixture was filtered to yield 1.76 kg of crystalshaving a succinic acid content of 96.7%. Drying of the crystals in avacuum drier produced 1.68 kg of succinic acid.

<Preparation of 1,4-butanediol>

From the biomass-resource-derived succinic acid obtained by theabove-described process, 1,4-butanediol was prepared in a known manner.Such 1,4-butanediol was obtained by the process as described below.

A mixture of 100 parts by weight of biomass-resource-derived succinicacid, 317 parts by weight of methanol and 2 parts by weight ofconcentrated sulfuric acid (97%) was stirred for 2 hours under reflux.After cooling, 3.6 parts by weight of sodium hydrogen carbonate wasadded to the reaction mixture, followed by stirring at 60° C. for 30minutes. After distillation under normal pressure and filtration of thedistillation residue, distillation was conducted under reduced pressureto yield dimethyl succinate (yield: 93%). In the presence of 15 parts byweight of a CuO—ZnO catalyst (T-8402, product of Süd-chemie), 100 partsby weight of the resulting dimethyl succinate was heated to 230° C. in 1hour in an autoclave (HASTELLOY C) having a capacity about 4 times thevolume of the dimethyl succinate charged while stirring under hydrogenpressure of 5 MPa. The reaction mixture was then stirred for 9 hours at230° C. under hydrogen pressure of 15 MPa. The reaction mixture wascooled and then degasified. The catalyst was filtered off from thereaction mixture. The filtrate was distilled under reduced pressure toyield purified 1,4-butanediol (yield: 81%). The purified 1,4-butanediolthus prepared contained 0.7 ppm of nitrogen atoms, but it contained nosulfur atoms. In addition, 1,4-butanediol contained 1000 ppm of2-(4-hydroxybutyloxy)tetrahydrofuran as an oxidation product.

<Preparation of Polyester and Pellets Thereof by UsingBiomass-Resource-Derived Succinic Acid Having a Nitrogen Atom Content of5 Ppm and a Sulfur Atom Content of 0.2 ppm>

Example 1

A reactor equipped with a stirrer, nitrogen gas inlet, heater,thermometer, and pressure reduction exhaust port was charged with 100parts by weight of biomass-resource-derived succinic acid (YI=2.5)having a nitrogen atom content of 5 ppm and a sulfur atom content of 0.2ppm, 88.5 parts by weight of industrial-grade 1,4-butanediolmanufactured by Mitsubishi Chemical, 0.37 part by weight of malic acid,and 5.4 parts by weight of a 88% aqueous solution of lactic acid having0.98 wt. % of germanium dioxide dissolved therein as a catalyst. Afterpressure reduction (ultimate vacuum: 0.2 kPa), a pressure recoveryoperation to atmospheric pressure was performed three times with anitrogen gas, whereby the atmosphere in the system became a nitrogenone.

The temperature in the system was then raised to 220° C. while stirringat 150 rpm and reaction was conducted at this temperature for 1 hour.The temperature was then raised to 230° C. in 30 minutes and at the sametime, the pressure was reduced to 0.07×10³ Pa in 1.5 hours. The reactionwas conducted for 1.8 hours under the same degree of pressure reduction.After pressure reduction, the stirring rotation speed of the stirrer wasreduced in stages to 150 rpm, 60 rpm and 40 rpm and the rotation speedfor 30 minutes prior to the completion of the polymerization was set at6 rpm. The polyester thus obtained was withdrawn in the form of strandsfrom the bottom of the reactor at 220° C. After the strands were causedto go into water of 10° C., they were cut into white pellets (yellownessdegree YI: 11). The white polyester pellets thus obtained had a minimumdiameter of 2 mm and maximum diameter of 3.5 mm. Drying of the pelletsat 80° C. for 8 hours under vacuum yielded pellets having a watercontent of 358 ppm. The polyester after drying had a nitrogen atomcontent of 2 ppm and a sulfur atom content of 0.1 ppm and the polyesterhad a reduced viscosity (ηsp/c) of 2.5 and an amount of terminalcarboxyl groups of 26 equivalents/metric ton. The polyester (0.5 g) thusobtained was dissolved uniformly in 1 dL of phenol/tetrachloroethane(1/1 (mass ratio) mixture) at room temperature.

The resulting dry pellets were stored for a half year in a bag made of apolyester/aluminum/polyethylene composite film under light shieldingcondition, but a marked deterioration in tensile elongation property ofthe pellets was not observed.

When the pellets were dried by heating at 100° C. for 72 hours undervacuum in order to reduce its water content further, coloration of thepolymer was observed, suggesting that drying for a long period of timeis not preferred.

Example 2

In a similar manner to that employed in Example 1 except for the use of100 parts by weight of the biomass-resource-derived succinic acid ofExample 1 having a nitrogen atom content of 5 ppm and a sulfur atomcontent of 0.2 ppm, 32 parts by weight of industrial-grade adipic acidmanufactured by Asahi Kasei, 111.6 parts by weight of industrial-grade1,4-butanediol manufactured by Mitsubishi Chemical, 0.48 part by weightof malic acid, and 7.2 parts by weight of a 88% aqueous solution oflactic acid having germanium dioxide dissolved therein in aconcentration of 0.98% by weight in advance as a catalyst, white pellets(yellowness degree YI: 13) similar to those obtained in Example 1 wereobtained (reduced viscosity (ηsp/c): 2.4, an amount of terminal carboxylgroup: 22 equivalents/metric ton). The polymerization reaction timeunder reduced pressure of 0.07×10³ Pa was 1.6 hours. The polyester (0.5g) thus obtained was dissolved uniformly in 1 dL ofphenol/tetrachloroethane (1/1 (mass ratio) mixture) at room temperature.

Example 3

Under similar conditions to those employed in Example 2 except for theuse of 100 parts by weight of the biomass-resource-derived succinic acidof Example 1 having a nitrogen atom content of 5 ppm and a sulfur atomcontent of 0.2 ppm, 81.4 parts by weight of industrial-grade1,4-butanediol manufactured by Mitsubishi Chemical, 6.3 parts by weightof ethylene glycol, 0.37 part by weight of malic acid, and 5.4 parts byweight of a 88% aqueous solution of lactic acid having germanium dioxidedissolved therein in a concentration of 0.98% by weight in advance as acatalyst, white pellets similar to those obtained in Example 1 wereobtained (reduced viscosity (ηsp/c): 2.4, an amount of terminal carboxylgroup: 21 equivalents//metric ton). The polyester (0.5 g) thus obtainedwas dissolved uniformly in 1 dL of phenol/tetrachloroethane (1/1 (massratio) mixture) at room temperature.

Example 4

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of the biomass-resource-derived succinic acidof Example 1 having a nitrogen atom content of 5 ppm and a sulfur atomcontent of 0.2 ppm, 81.4 parts by weight of industrial-grade1,4-butanediol manufactured by Mitsubishi Chemical, 12.3 parts by weightof 1,4-cyclohexanedimethanol, 0.37 part by weight of malic acid, and 5.4parts by weight of a 88% aqueous solution of lactic acid having 0.98 wt.% of germanium dioxide dissolved therein in advance as a catalyst, whitepellets similar to those obtained in Example 1 were obtained (reducedviscosity (ηsp/c): 2.6, an amount of terminal carboxyl group: 17equivalents/metric ton). The polymerization reaction time under reducedpressure of 0.07×10³ Pa was 3.8 hours. The polyester (0.5 g) thusobtained was dissolved uniformly in 1 dL of phenol/tetrachloroethane(1/1 (mass ratio) mixture) at room temperature.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 12 Ppm and a Sulfur Atom Content of 5 ppm>

Example 5

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of biomass-resource-derived succinic acid(yellowness degree YI: 7) having a nitrogen atom content of 12 ppm and asulfur atom content of 5 ppm instead of 100 parts by weight of thebiomass-resource-derived succinic acid of Example 1 having a nitrogenatom content of 5 ppm and a sulfur atom content of 0.2 ppm, whitepellets similar to those obtained in Example 1 were obtained. Thepolymerization reaction time under reduced pressure of 0.07×10³ Pa was 2hours.

The polyester thus obtained (yellowness degree YI: 22) had a nitrogenatom content of 3.6 ppm, a sulfur atom content of 2.6 ppm, a reducedviscosity (ηsp/c) of 2.3 and an amount of terminal carboxyl groups of 19equivalents/metric ton. The polyester (0.5 g) thus obtained wasdissolved uniformly in 1 dL of phenol/tetrachloroethane (1/1 (massratio) mixture) at room temperature.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 16 Ppm and a Sulfur Atom Content of 2 ppm>

Example 6

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of biomass-resource-derived succinic acid(yellowness degree YI: 3) having a nitrogen atom content of 16 ppm and asulfur atom content of 2 ppm instead of 100 parts by weight of thebiomass-resource-derived succinic acid of Example 1 having a nitrogenatom content of 5 ppm and a sulfur atom content of 0.2 ppm, whitepellets similar to those obtained in Example 1 were obtained. Thepolymerization reaction time under reduced pressure of 0.07×10³ Pa was2.1 hours.

The polyester thus obtained (yellowness degree YI: 19) had a nitrogenatom content of 3.4 ppm, a sulfur atom content of 1.4 ppm, a reducedviscosity (ηsp/c) of 2.4 and an amount of terminal carboxyl groups of 15equivalents/metric ton. The polyester (0.5 g) thus obtained wasdissolved uniformly in 1 dL of phenol/tetrachloroethane (1/1 (massratio) mixture) at room temperature.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 115 ppm and a Sulfur Atom Content of 0.3 ppm>

Example 7

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of biomass-resource-derived succinic acidhaving a nitrogen atom content of 115 ppm and a sulfur atom content of0.3 ppm instead of 100 parts by weight of the biomass-resource-derivedsuccinic acid of Example 1 having a nitrogen atom content of 5 ppm and asulfur atom content of 0.2 ppm, pellets similar to those obtained inExample 1 were prepared. The polymerization reaction time under reducedpressure of 0.07×10³ Pa was 2.9 hours.

The polyester thus obtained (yellowness degree YI: 23) had a nitrogenatom content of 19 ppm, a sulfur atom content of 0.2 ppm, a reducedviscosity (ηsp/c) of 2.5 and an amount of terminal carboxyl groups of 19equivalents/metric ton. The polyester (0.5 g) thus obtained wasdissolved uniformly in 1 dL of phenol/tetrachloroethane (1/1 (massratio) mixture) at room temperature.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 180 ppm and a Sulfur Atom Content of 1 ppm>

Example 8

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of biomass-resource-derived succinic acidhaving a nitrogen atom content of 180 ppm and a sulfur atom content of 1ppm instead of 100 parts by weight of the biomass-resource-derivedsuccinic acid of Example 1 having a nitrogen atom content of 5 ppm and asulfur atom content of 0.2 ppm, polyester pellets similar to thoseobtained in Example 1 were obtained. The polymerization reaction timeunder reduced pressure of 0.07×10³ Pa was 2.6 hours.

The polyester thus obtained (yellowness degree YI: 37) had a nitrogenatom content of 22 ppm, a sulfur atom content of 0.6 ppm, a reducedviscosity (ηsp/c) of 2.5 and an amount of terminal carboxyl groups of 19equivalents/metric ton. The polyester (0.5 g) thus obtained wasdissolved uniformly in 1 dL of phenol/tetrachloroethane (1/1 (massratio) mixture) at room temperature.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 230 ppm and a Sulfur Atom Content of 1 ppm>

Example 9

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of biomass-resource-derived succinic acid(yellowness degree YI: 11) having a nitrogen atom content of 230 ppm anda sulfur atom content of 1 ppm instead of 100 parts by weight of thebiomass-resource-derived succinic acid of Example 1 having a nitrogenatom content of 5 ppm and a sulfur atom content of 0.2 ppm, polyesterpellets similar to those obtained in Example 1 were prepared. Thepolymerization reaction time under reduced pressure of 0.07×10³ Pa was2.6 hours.

The polyester thus obtained (yellowness degree YI: 39) had a nitrogenatom content of 27 ppm, a sulfur atom content of 0.6 ppm, a reducedviscosity (ηsp/c) of 2.4 and an amount of terminal carboxyl groups of 19equivalents/metric ton. The polyester (0.5 g) thus obtained wasdissolved uniformly in 1 dL of phenol/tetrachloroethane (1/1 (massratio) mixture) at room temperature.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 30 ppm and a Sulfur Atom Content of 18 ppm>

Example 10

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of biomass-resource-derived succinic acidhaving a nitrogen atom content of 30 ppm and a sulfur atom content of 18ppm instead of 100 parts by weight of the biomass-resource-derivedsuccinic acid of Example 1 having a nitrogen atom content of 5 ppm and asulfur atom content of 0.2 ppm, polyester pellets similar to thoseobtained in Example 1 were prepared. The polymerization reaction timeunder reduced pressure of 0.07×10³ Pa was 3.3 hours.

The brown polyester thus obtained (yellowness degree YI: 42) had areduced viscosity (ηsp/c) of 2.4 and an amount of terminal carboxylgroups of 18 equivalents/metric ton. The polyester (0.5 g) thus obtainedwas dissolved almost uniformly in 1 dL of phenol/tetrachloroethane (1/1(mass ratio) mixture) at room temperature, but trace insoluble matterswere observed.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 5 ppm and a Sulfur Atom Content of 0.2 PPMand Biomass-Resource-Derived 1,4-butanediol Having a Nitrogen AtomContent of 0.7 ppm>

Example 11

Under similar conditions to Example 1 except for the use of 88.5 partsby weight of biomass-resource-derived 1,4-butanediol having a nitrogenatom content of 0.7 ppm instead of 88.5 parts by weight of theindustrial-grade 1,4-butanediol of Example 1 manufactured by MitsubishiChemical, polyester pellets similar to those obtained in Example 1 wereobtained. The polymerization reaction time under reduced pressure of0.07×10³ Pa was 3 hours.

The polyester thus obtained (yellowness degree YI: −1) had a reducedviscosity (ηsp/c) of 2.5 and an amount of terminal carboxyl groups of 21equivalents/metric ton. The polyester (0.5 g) thus obtained wasdissolved uniformly in 1 dL of phenol/tetrachloroethane (1/1 (massratio) mixture) at room temperature.

Example 12

A reactor equipped with a stirrer, nitrogen gas inlet, heater,thermometer, and pressure reduction exhaust port was charged with 100parts by weight of the biomass-resource-derived succinic acid of Example1 having a nitrogen atom content of 5 ppm and a sulfur atom content of0.2 ppm, 80.4 parts by weight of biomass-resource-derived 1,4-butanetholhaving a nitrogen atom content of 0.7 ppm, and 0.37 part by weight ofmalic acid. After pressure reduction (ultimate vacuum: 0.2 kPa), apressure recovery operation to atmospheric pressure was performed threetimes with a nitrogen gas, whereby an atmosphere in the system waschanged to a nitrogen one.

The temperature in the system was then raised to 220° C. while stirringand reaction was conducted at this temperature for 1 hour. Then, acatalyst solution obtained by diluting 0.11 part by weight oftetra-n-butyl titanate in 0.4 part by weight of butanol was added to thereaction system. The temperature was raised to 230° C. in 30 minutes,while the pressure was reduced to 0.07×10³ Pa in 1.5 hours. The reactionwas conducted for 2 hours under the same degree of pressure reduction.While controlling the resin temperature to 220° C., the polyester thusobtained was withdrawn in the form of strands from the bottom of thereactor at 220° C. After the strands were caused to go into water of 10°C., they were cut by a cutter, whereby pellets similar to Example 1(reduced viscosity (ηsp/c) of 2.5 and an amount of terminal carboxylgroups of 12 equivalents/metric ton) were obtained. The polyester (0.5g) thus obtained was dissolved uniformly in 1 dL ofphenol/tetrachloroethane (1/1 (mass ratio) mixture) at room temperature.

<Polyester Prepared Using Petroleum-Derived Succinic Acid ContainingNeither Nitrogen Atom Nor Sulfur Atom and Biomass-Resource-Derived1,4-butanediol Containing a Nitrogen Atom Content of 0.7 ppm>

Example 13

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of succinic acid (industrial grade,manufactured by Kawasaki Kasei Chemicals, yellow ness degree YI: 2)containing neither nitrogen atom nor sulfur atom instead of the succinicacid of Example 1 and 88.5 parts by weight of biomass-resource-derived1,4-butanediol instead of the petroleum-derived 1,4-butanediol ofExample 1, polyester pellets similar to those obtained in Example 1 wereobtained. The polymerization reaction time under reduced pressure of0.07×10³ Pa was 3.4 hours.

The polyester thus obtained (yellowness degree YI: 7) had a nitrogenatom content of 0.5 ppm, a reduced viscosity (ηsp/c) of 2.5 and anamount of terminal carboxyl groups of 28 equivalents/metric ton. Thepolyester (0.5 g) thus obtained was dissolved uniformly in 1 dL ofphenol/tetrachloroethane (1/1 (mass ratio) mixture) at room temperature.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 3 ppm and a Sulfur Atom Content of 34 ppm>

Example 14

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of biomass-resource-derived succinic acidhaving a nitrogen atom content of 3 ppm and a sulfur atom content of 34ppm instead of the succinic acid of example 1, polyester pellets similarto those obtained in Example 1 were prepared. The polymerizationreaction time under reduced pressure of 0.07×10³ Pa was 7 hours.

The polyester thus obtained (yellowness degree YI: 38) had a reducedviscosity (ηsp/c) of 2.4 and an amount of terminal carboxyl groups of 30equivalents/metric ton. The polyester (0.5 g) thus obtained wasdissolved in 1 dL of phenol/tetrachloroethane (1/1 (mass ratio) mixture)at room temperature, but a small amount of insoluble matters wasobserved.

Polyester Prepared Using Petroleum-Derived and Nitrogen-Atom-FreeDimethyl Terephthalate and Biomass-Resource-Derived 1,4-butanediolHaving a Nitrogen Atom Content of 0.7 ppm>

Example 15

A reactor equipped with a stirrer, nitrogen gas inlet, heater,thermometer, and pressure reduction exhaust port was charged with 132parts by weight of the dimethyl terephthalate, 74 parts by weight ofbiomass-resource-derived 1,4-butanediol having a nitrogen atom contentof 0.7 ppm, and 1.7 parts by weight of a 1,4-butanediol solution having6 wt. % of tetrabutyl titanate dissolved in advance therein as acatalyst. By purging with nitrogen under reduced pressure, theatmosphere in the system was changed to a nitrogen one.

After the temperature in the reaction system was raised to 150° C. understirring, reaction was conducted for 3 hours while heating to 215° C.The temperature was then raised to 245° C. and at the same time, thepressure was reduced to 0.07×10³ Pa in 1.5 hours. Without changing thedegree of pressure reduction, the reaction was conducted for 1.5 hoursand polymerization reaction was completed. The polyester thus obtainedwas withdrawn in the form of strands from the bottom of the reactor.After the strands were caused to go into water of 10° C., they were cutby a cutter, whereby pellets similar to those obtained in Example 1(yellowness degree YI: 0.4) were obtained.

The polyester thus obtained had a nitrogen atom content of 0.4 ppm, areduced viscosity (ηsp/c) of 1.2 and an amount of terminal carboxylgroups of 21 equivalents/metric ton. The resulting polyester (0.5 g) wasdissolved uniformly in 1 dL of phenol/tetrachloroethane (1/1 (massratio) mixture) at room temperature.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 660 ppm and a Sulfur Atom Content of 330 ppm>

Comparative Example 1

Under similar polycondensation conditions to those employed in Example 1except for the use of 100 parts by weight of biomass-resource-derivedsuccinic acid (yellowness degree YI: 8) having a nitrogen atom contentof 660 ppm and a sulfur atom content of 330 ppm instead of the succinicacid used in Example 1, polyester was prepared. Polymerization reactionwas performed for 2.5 hours under reduced pressure of 0.07×10³ Pa, butthe polyester thus obtained was colored dark brown (yellowness degreeYI: 60 or greater).

The dark brown polyester thus obtained had a nitrogen atom content of 54ppm, a sulfur atom content of 16 ppm and reduced viscosity (ηsp/c) of0.7 and an amount of terminal carboxyl groups of 139 equivalents/metricton.

<Polyester Prepared Using Biomass-Resource-Derived Succinic Acid Havinga Nitrogen Atom Content of 850 ppm and a Sulfur Atom Content of 290 ppm>

Comparative Example 2

Under similar conditions to those employed in Example 1 except for theuse of 100 parts by weight of biomass-resource-derived succinic acid(yellowness degree YI; 8) having a nitrogen atom content of 850 ppm anda sulfur atom content of 290 ppm instead of the succinic acid used inExample 1, polyester pellets were prepared. Polymerization reaction wasperformed for 2.5 hours under reduced pressure of 0.07×10³ Pa, but thepolyester thus obtained was colored dark brown (yellowness degree YI: 60or greater).

The dark brown polyester thus obtained had a nitrogen atom content of 51ppm, a sulfur atom content of 16 ppm and reduced viscosity (ηsp/c) of1.1 and an amount of terminal carboxyl groups of 69 equivalents/metricton.

Comparative Example 3

Under similar polycondensation conditions to those employed in Example12 except that the reaction temperature after the addition of a catalystobtained by diluting tetra-n-butyl titanate in butanol was changed from230° C. to 240° C., polyester and pellets thereof was prepared.Polymerization time under reduced pressure of 0.07×10³ Pa was 3 hours.The polyester (yellowness degree YI: 19) after drying had a reducedviscosity (ηsp/a) of 2.4 and an amount of terminal carboxyl groups of 54equivalents/metric ton. The resulting polyester (0.5 g) was dissolvedalmost uniformly in 1 dL of phenol/tetrachloroethane (1/1 (mass ratio)mixture) at room temperature, but trace insoluble matters were observed.

Comparative Example 4

Under similar conditions to those employed in Example 1 except that 0.74part by weight of malic acid was charged instead of 0.37 part by weightof malic acid, white polyester pellets similar to Example 1 wereprepared. The polymerization time under reduced pressure of 0.07×10³ Pawas 1.1 hours. The polyester thus obtained had a reduced viscosity(ηsp/c) of 3.2 and an amount of terminal carboxyl groups of 63equivalents/metric ton. The resulting polyester (0.5 g) was dissolvedalmost uniformly in 1 dL of phenol/tetrachloroethane (1/1 (mass ratio)mixture) at room temperature, but a small amount of insoluble matterswas observed.

Comparative Example 5

By using a commercially available petroleum-derived raw materialcontaining neither nitrogen atom nor sulfur atom instead of the succinicacid prepared by the fermentation process in Example 1, a polyester wasprepared. More specifically, the polyester similar to that prepared inExample 1 was prepared in a similar manner to that employed in Example 1except that industrial-grade succinic acid manufactured by KawasakiKasei chemicals and industrial grade 1,4-butanediol manufactured byMitsubishi Chemical. Neither nitrogen atom nor sulfur atom was detectedfrom the polyester thus prepared.

It has been found from Examples and Comparative Examples, thatcoloration of a polyester or inhibition against polymerization tends tobe severe with an increase in the content of a nitrogen atom or sulfuratom in the polyester. In particular, with an increase in the content ofa nitrogen atom, the coloration of the polymer tends to be severer. Whena sulfur atom content exceeds a certain amount or preparation isperformed at high temperatures, an increase in the amount of terminalcarboxyl groups occurs and an amount of insoluble matters in an organicsolvent, which are presumed to be generated by the partial gelation,tends to be greater. It is known that mixing of such insoluble mattersin the product damages the appearance of the product or causesdeterioration of its physical properties.

Physical Property Evaluation Example 1 <Evaluation of Storage StabilityBased on Water Content in Pellets>

Storage stability of the polyester pellets prepared in example 1 wasevaluated by hermetically sealed pellets in a bag (bag A1) made of apolyester/aluminum/polyethylene composite film. Storage stability wasevaluated by a method of hermetically sealed pellets having respectivewater contents in a bag (bag A1) made of polyester/aluminum/polyethylenecomposite film, retaining it in an oven of 40° C., and measuring asolution viscosity (reduced viscosity (ηsp/c)) of each sample for acertain period. Arrival time of the sample to a predetermined reducedviscosity (ηsp/c) as a result of hydrolysis during storage under heatingis shown in Table 1.

Example 16

A water content in the polyester pellets prepared in Example 1 wasadjusted to 358 ppm by maintaining the pellets under the conditions of23° C. and 50% RH for a predetermined time. The resulting pellets werehermetically sealed in a bag (bag A1) made of apolyester/aluminum/polyethylene composite film and retained the bag inan oven of 40° C. The solution viscosity (reduced viscosity (ηsp/c)) ofeach of the samples was measured for a certain period. Arrival time ofthe sample to a predetermined reduced viscosity (ηsp/c) as a result ofhydrolysis during storage under heating is shown in Table 1.

Example 17

In a similar manner to Example 16, a water content in the polyesterpellets prepared in Example 1 was adjusted to 472 ppm and storagestability thereof was evaluated. The results are shown in Table 1.

Example 18

In a similar manner to Example 16, a water content in the polyesterpellets prepared in Example 1 was adjusted to 796 ppm and storagestability thereof was evaluated. The results are shown in Table 2.

Example 19

In a similar manner to Example 16, a water content in the polyesterpellets prepared in Example 1 was adjusted to 1086 ppm and storagestability thereof was evaluated. The results are shown in Table 1.

Comparative Example 6

In a similar manner to Example 16, a water content in the polyesterpellets prepared in Example 1 was adjusted to 3151 ppm and storagestability thereof was evaluated. The results are shown in Table 1.

It has been found from Table 1 that a drastic reduction in the reducedviscosity (ηsp/c) during storage occurs when the water content in thepellets during storage exceeds 3000 ppm. Deterioration in the physicalproperties of the film due to reduction in the reduced viscosity (ηsp/c)is shown in Table 2.

TABLE 1 <Arrival time to predetermined reduced viscosity (ηsp/c) byhermetically-sealed storage at 40° C.> Reduced viscosity (ηsp/c) 2.4 2.22.0 1.7 1.6 Example 16 Polyester pellets 0 h 2347 h 3355 h — — having awater content of 358 ppm Example 17 Polyester pellets 0 h 2011 h 3019 h— — having a water content of 472 ppm Example 18 Polyester pellets 0 h1482 h 2851 h — — having a water content of 796 ppm Example 19 Polyesterpellets 0 h 1314 h 2682 h — — having a water content of 1086 ppmComparative Polyester pellets 0 h 474 h 810 h 2011 2682 Example 6 havinga water h h content of 3151 ppm

<Influence of Viscosity Reduction on Physical Properties of Film>

Blown film extrusion of the polyester prepared in Example 1 was carriedout. A film having a thickness of 20 μm was formed under the extrusionconditions of an extrusion temperature of 160° C. and blow ratio of 2.5.Deterioration behavior of a physical property (tensile elongation atbreak) due to viscosity reduction of the film thus formed is shown inTable 2. It is presumed that a reduction in reduced viscosity leads toreduction in tensile elongation at break so that a polyester having areduced viscosity has poor film formability.

TABLE 2 Reduced viscosity (ηsp/c) 2.4 2.1 2.0 1.9 1.6 1.3 0.8 Tensileelongation 410 390 394 320 221 105 0 at break (MD direction (%)) (Note)Tensile test: in accordance with JIS Z1702 MD: flow direction at thetime of film formation

Physical Property Evaluation Example 2 <Influence of Amount of TerminalCarboxylic Acid on Hydrolysis Resistance>

The polyester pellets obtained in Example 1, Example 12 and ComparativeExample 3 were charged in a thermo-hygrostat set at 50° C. and 90% RH.War a certain period, the samples were taken out and solution viscosityand amount of terminal carboxylic acid of each of them were measured.The results are shown in Table 3. It has been found from these resultsthat an amount of the terminal carboxylic acid exceeding 50equivalents/metric ton leads to marked deterioration in the hydrolysisresistance of the polyester and the resulting polyester is not suitedfor practical use because of low storage properties.

TABLE 3 Hydrolysis resistance test at 50° C. and 90% RH Sample Storedfor 0 day 7 days 21 days 28 days Example 1 Reduced viscosity 2.5 2.0 1.71.2 (ηsP/c) Amount of terminal 26 34 40 57 carboxylic acid(equivalent/metric ton) Example 12 Reduced viscosity 2.5 2.4 2.3 2.0(ηsp/c) Amount of terminal 12 11 13 19 carboxylic acid(equivalent/metric ton) Comparative Reduced viscosity 2.4 1.9 1.5 1.0Example 3 (ηsp/c) Amount of terminal 54 66 76 100 carboxylic acid(equivalent/metric ton)

Physical Property Evaluation Example 3 <Evaluation of Biodegradability>

Each of the polyesters prepared in Example 1 and Comparative Example 5was formed into a film having a thickness of 20 μm by using a blown filmextruder at an extrusion temperature of 160° C. and blow ratio of 2.5.The film thus formed was cut into a size of 5 cm×18 cm and was buried inthe soil. Biodegradability test was carried out by measuring a weightreduction percentage of the film after 1 month, 2 months, 3 months and 6months, respectively. The results are shown in Table 4. It has beenconfirmed from Table 4 that the polyester using succinic acid preparedby the fermentation process had a high biodegradation rate in the soil.

<Biodegradability Test in the Soil>

The film formed by the above-described method was cut into a size of 5cm×18 cm and buried in the soil. A weight reduction percentage of thefilm after 1 month, 2 months, 3 months and 6 months was measuredrespectively. The results are shown in Table 4.

TABLE 4 Results of weight reduction percentage of film Average weightreduction percentage (%) Sample 1 month 2 months 3 months 6 monthsPolyester prepared in 5 9 10 31 Comparative Example 5 Polyester preparedin 27 64 77 80 Example 1

Referential Example 6

Molding or forming examples and various physical properties ofpolyesters prepared in Example 1 and various compositions thereof areshown below as a referential example.

<Preparation of Composition>

Compositions 1 and 2 were prepared in accordance with the respectivemixing ratios (wt. %) shown in Table 5. These compositions were preparedat a kneading temperature of 190° C. by using a twin-screw extruder(KZW15), product of TECHNOVEL.

TABLE 5 Composition 1 Composition 2 Polyester of Example 1 70 70 Talc 30Ecoflex 30 (Note) Talc: “PKP-538”, product of Fuji Talc Ecoflex: productof BASF Japan

Compositions 3 to 5 were prepared in accordance with the mixing ratios(wt. %) shown Table 6. The compositions were prepared at a kneadingtemperature of 190° C. by using a Labo Plastomill, product of Toyo SeikiSeisaku-sho.

TABLE 6 Composition 3 Composition 4 Composition 5 Polyester of 75 50 25Example 1 Polylactic acid 25 50 75 (Note) Polylactic acid: “LACEAK-400”, product of Mitsui Chemical

<Injection Molding>

The samples shown in Table 7 were injection molded using a benchtopinjection molder, MINIMAX, product of CSI. The molding temperature wasset at 200° C. Evaluation results of physical properties are also shownin Table 7. Evaluation of each sample was carried out at 23° C. and 50%RH.

TABLE 7 Com- Com- Com- Com- Polyester position position positionposition Unit of Example 1 1 2 3 4 Izod kJ/m² 8.9 5.0 9.5 5.2 3.0 impactstrength Note) Izod impact test: in accordance with JIS K7110(unnotched)

<Sheet Formation>

The samples shown in Table 8 were formed into a sheet by using a T-diefilm forming machine. The sheet having a thickness of 500 μm was formedat a forming temperature of 200° C. and roll temperature of 30° C.Evaluation results of physical properties are also shown in Table 8.Evaluation of each physical property was made at 23° C. and 50% RH.

TABLE 8 Polyester of Unit Direction Example 1 Composition 1 Tensileyield MPa MD 35 40 strength TD 36 33 Tensile strength MPa MD 38 45 atbreak TD 30 25 Tensile % MD 310 320 elongation at TD 260 30 breakFlexural strength MPa MD — 36 TD — 42 Flexural modulus MPa MD — 2850 TD— 3450 (Note) Tensile test: in accordance with JIS K7113 Dumbbell No. 2was used (extension rate: 50 mm/min) Flexural test: in accordance withJIS K7203 MD: Flow direction at the time of sheet formation TD:direction perpendicular to the flow

<Film Formation>

Blown film extrusion was performed using the samples shown in Table 9.The film having a thickness of 20 μm was formed at a forming temperatureof 160° C. and blow ratio of 2.5. Evaluation results of the physicalproperties are also shown in Table 9. Evaluation of each of the physicalproperties was made at 23° C. and 50% RH.

TABLE 9 Polyester of Unit Direction Example 1 Composition 5 Tensileyield MPa MD 35 20 strength TD 32 20 Tensile strength MPa MD 60 60 atbreak TD 25 60 Tensile % MD 410 650 elongation at TD 100 730 break(Note) Tensile test: in accordance with JIS Z1702 MD: Flow direction atthe time of sheet formation TD: Direction perpendicular to the flow

<Foam Molding>

The polyester prepared in Example 1 was pressed at 190° C. and 10 MPainto a sheet having a thickness of 1 mm. The sheet thus obtained, in thesolid form, was charged in a pressure vessel equipped with valves. Thetemperature in the pressure vessel was raised to 100° C. by an outsideheating source and at the same time, carbon dioxide was charged in thepressure vessel. At the time of charging, the pressure was raised to 15MPa by pumping. The temperature and pressure were kept at 100° C. and 15MPa, respectively, for 2 hours. Then, the valves of the pressure vesselwere all opened to release the pressure in the pressure bottle at aburst, whereby a foamed product was obtained. The foamed product thusobtained did not emit bubbles even pressed in water and thus had a highclosed-cell foam ratio.

The present invention was so far described specifically based on someembodiments. It is apparent to those skilled in the art that variouschanges or modifications can be made without departing from theintention and scope of the present invention. The present application isbased on Japanese Patent Application (Japanese Patent Application No.2005-125318) filed on Apr. 22, 2005, Japanese Patent Application(Japanese Patent Application No. 2005-125319) filed on Apr. 22, 2005,Japanese Patent Application (Japanese Patent Application No.2005-125320) filed on Apr. 22, 2005, Japanese Patent Application(Japanese Patent Application No. 2005-125321) filed on Apr. 22, 2005,Japanese Patent Application (Japanese Patent Application No.2005-127757) filed on Apr. 26, 2005, Japanese Patent Application(Japanese Patent Application No. 2005-127761) filed on Apr. 26, 2005,Japanese Patent Application (Japanese Patent Application No.2005-128886) filed on Apr. 27, 2005, Japanese Patent Application(Japanese Patent Application No. 2005-375353) filed on Dec. 27, 2005,Japanese Patent Application (Japanese Patent Application No.2005-375354) filed on Dec. 27, 2005, and Japanese Patent Application(Japanese Patent Application No. 2005-375355) filed on Dec. 27, 2005,which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The birth of the polyester of the present invention and backgroundthereof will next be described in detail. In a large cycle on the earthin the atmosphere, the appearance of the polyester of the presentinvention can be evaluated from many standpoints such as conservation ofearth's environment, resource saving, pollution prevention, aestheticenvironmental protection and new-technology-oriented development.

The polyester of the present invention is characterized by its distinctdifference in the significance of existence in the earth's environmentfrom the conventional polyesters derived from underground fossil fuels,for example, petroleum-resource-derived polyesters.

In particular, a diol unit or dicarboxylic acid unit obtained fromnatural materials, which have vegetated under the earth's environment inthe present atmosphere, by the fermentation process or the like is usedas a monomer of the polyester so that raw materials are available at avery low cost. In addition, they can be supplied stably with less riskbecause the production of plants can be enhanced artificially,systematically and arbitrarily so that plant raw materials can beproduced in various regions or various countries without limiting theproduction site. Moreover, since a cycle from raw materials of thepolyester to the final discarding stage of it after use, morespecifically, a cycle from procurement of monomers and synthesis ofpolyester to biodegradation of it is carried out based only on thenatural process under the earth's environment in the atmosphere, thepolyester of the present invention can give consumers a feeling ofreliability and security. These are of course non-negligible andimportant backgrounds in the technological development, growth of theindustry, and expansion of consumer society related to the polyester.

Response to the demands of the present age built on technologicalprogress however mainly contributes to the birth of the polyester of thepresent invention. Countermeasures against worsening of the earth'senvironment due to, for example, a so-called greenhouse effect by a CO₂gas, countermeasures against a sense of crisis over wasteful use anddepletion of petroleum resources, and recent advance in peripheraltechnology, which is a more important reason, more specifically, markedadvance of biotechnology such as fermentation technology enable thebirth of the polyester of the present invention. In the first place, thepolyester of the present invention is produced by a method depending onthe vegetation in the atmosphere. In the production of raw materialplants by this method, a large amount of carbon dioxide is absorbed.This absorption amount is designated as Abs. The plants emit a smallamount of carbon dioxide and thermal energy during processing,fermentation and treatment, but a diol unit or a dicarboxylic acid canbe prepared therefrom easily. When the polyester of the presentinvention obtained by polymerization is buried in the ground, left inwater or left in seawater, it is decomposed by microorganisms and thelike and substantially releases water and carbon dioxide. This releaseamount is designated as Rel. There is a small difference between Abs andRel. In this sense, the difference between the absorbed amount andreleased amount of carbon dioxide in the atmosphere will be relativelysmall. This invention is advantageous not only in the balance betweenthe absorption and release of carbon dioxide as described above but alsoenergy balance. In the present invention intended to depend onvegetation, an increase in the amount of a CO₂ gas emitted newly to theatmosphere, which is the problem of the conventionalfossil-resource-dependent type polyester, can be prevented as much aspossible.

As secondary effects, the polyester material of the present inventionnot only has commendable physical properties, structure and function,but also is very eco-friendly and safe polyester. The process of it fromvegetation of raw materials to disappearance of them as described abovehas a potential possibility of actualizing a recycling society whichcannot be expected from the fossil-fuel-derived polyester. Thisprovides, in future production process of polyesters, a newrecycling-oriented polyester production process which is different ironwhat the conventional fossil-fuel-dependent polyester aims at. It is theplastic that meets the needs of the age and adopts the leading-agetechnology quickly and as a result, essentially changes the perceptionof the so-called plastic industries. It can be evaluated even as aninnovative plastic which can start the second plastic age based on therecent remarkable technological growth. The polyester of the presentinvention has thus a high potential evaluation and value so that itcontributes greatly to the expansion of application fields, growth andconsumption of a polyester as one typical example of plastic materials.

1-18. (canceled)
 19. A biomass-resource derived diol comprising anitrogen atom in an amount of 0.01 ppm to 50 ppm.
 20. Thebiomass-resource derived diol of claim 19, which is an aliphatic diolhaving 10 or less carbon atoms.
 21. The biomass-resource derived diol ofclaim 19, wherein a carbon number of the diol is an even number.
 22. Thebiomass-resource derived diol of claim 20, wherein a carbon number ofthe diol is an even number.
 23. The biomass-resource derived diol ofclaim 19, which further comprises a sulfur atom in an amount of 0.001ppm to 10 ppm.
 24. The biomass-resource derived diol of claim 20, whichfurther comprises a sulfur atom in an amount of 0.001 ppm to 10 ppm. 25.A polyester comprising: a diol unit containing the diol of claim 19; anda dicarboxylic acid unit, wherein a nitrogen content in the polyester,except nitrogen atoms covalently bonded in the functional groups of thepolyester, is 0.01 ppm to 50 ppm.
 26. A polyester comprising: a diolunit containing the diol of claim 20; and a dicarboxylic acid unit,wherein a nitrogen content in the polyester, except nitrogen atomscovalently bonded in the functional groups of the polyester, is 0.01 ppmto 50 ppm.
 27. The polyester of claim 25, which further comprises atleast one polyfunctional compound unit selected from the groupconsisting of tri- or higher functional polyhydric alcohols, tri- orhigher functional polycarboxylic acids, and tri- or higher functionaloxycarboxylic acids.
 28. The polyester of claim 26, which furthercomprises at least one polyfunctional compound unit selected from thegroup consisting of tri- or higher functional polyhydric alcohols, tri-or higher functional polycarboxylic acids, and tri- or higher functionaloxycarboxylic acids.